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Article / Updated 05-17-2023

Father's Day, celebrated in the United States on the third Sunday of June, got a jump start from the formation of Mother's Day. Credit for beginning Father's Day celebrations is given to Sonora Smart Dodd (1882—1978) of Spokane, Washington. At the turn of the century, Mother's Day observances were growing across the United States. The federal government had yet to recognize the holiday, but many states had adopted the third Sunday in May as a special celebration day honoring mothers. It was during a Mother's Day church service on June 20, 1909, that Sonora Smart Dodd was struck with the idea of creating a special holiday to honor fathers, too. When Dodd was 16, her mother died while giving birth to her sixth child, the last of five sons. Back then, like today, single parenthood was no easy task. By Dodd's account, though, her father, a Civil War veteran named William Jackson Smart, did a wonderful job. Because of this love and esteem, Dodd believed that her father deserved a special time of honor just like that given to mothers on Mother's Day. In 1909, Dodd approached the Spokane YMCA and the Spokane Ministerial Alliance and suggested that her father's birthday, June 5, become a celebration day for Father's Day. Because they wanted more time to prepare, the Ministerial Alliance chose June 19 instead. The first Father's Day was thus observed in the State of Washington on June 19, 1910. The idea of officially celebrating fatherhood spread quickly across the United States, as more and more states adopted the holiday. In 1924, President Calvin Coolidge recognized Father's Day as the third Sunday in June of that year and encouraged states to do the same. Congress officially recognized Father's Day in 1956 with the passage of a joint resolution. Ten years later, in 1966, President Lyndon Johnson issued a proclamation calling for the third Sunday in June to be recognized as Father's Day. In 1972, President Richard Nixon permanently established the observance of the third Sunday in June as Father's Day in the United States. Dodd lived to see her dream come to fruition. She died in 1978 at the age of 96.

View ArticleCheat Sheet / Updated 05-17-2023

The Graduate Record Examinations (GRE) is your gateway to getting into the graduate school of your choice, maybe even with a scholarship, which then opens the doors to your career path. This Cheat Sheet is a collection of tips and key information that can help you score well on the GRE, get into graduate school, and further your career goals.

View Cheat SheetCheat Sheet / Updated 05-15-2023

Taking the Series 7 exam, whether for the first time or the fourteenth, is a huge challenge and requires many hours of preparation. Use this cheat sheet to put your time to good use before the exam even begins and to be successful when it’s completed.

View Cheat SheetCheat Sheet / Updated 05-15-2023

Environmental science is a field of study focused on Earth’s environment and the resources it provides to every living organism, including humans. Environmental scientists focus on studying the environment and everything in it and finding sustainable solutions to environmental issues. In particular, this means meeting the needs of human beings (and other organisms) today without damaging the environment, depleting resources, or compromising the earth’s ability to meet the resource needs of the future. A sustainable solution to an environmental problem must be ecologically sound, economically viable, and culturally acceptable. This Cheat Sheet summarizes some key aspects of what environmental scientists study.

View Cheat SheetArticle / Updated 05-10-2023

Listen to the article:Download audio Whether you're leaving a tip at a restaurant or figuring out just how much those stylish shoes are on sale, you can't get away from percentages. While there are numerous percentage calculators online, it's helpful to know how to calculate the percentage of a number by doing some quick math in your head, without any digital assistance. What is percentage? Before learning how to figure out percentages, it's helpful to know that the word percentage comes from the word percent. If you split the word percent into its root words, you see “per” and “cent.” Cent is an old European word with French, Latin, and Italian origins meaning “hundred." So, percent is translated directly to “per hundred.” If you have 87 percent, you literally have 87 per 100. If it snowed 13 times in the last 100 days, it snowed 13 percent of the time. Of course, if you have 100 percent of anything, you have all of it. Saying that 50 percent of the students are girls is the same as saying that 1/2 of them are girls. Or if you prefer decimals, it’s the same thing as saying that 0.5 of all the students are girls. This example shows you that percents, like fractions and decimals, are just another way of talking about parts of the whole. In this case, the whole is the total number of children in the school. You don’t literally have to have 100 of something to use a percent or figure percentage. You probably won’t ever really cut a cake into 100 pieces, but that doesn’t matter. The values are the same. Whether you’re talking about cake, a dollar, or a group of children, 50 percent is still half, 25 percent is still one-quarter, 75 percent is still three-quarters, and so on. Any percentage smaller than 100 percent means less than the whole — the smaller the percentage, the less you have. You probably know this fact well from the school grading system. If you get 100 percent, you get a perfect score. And 90 percent is usually A work, 80 percent is a B, 70 percent is a C, and, well, you know the rest. Of course, 0 percent means “0 out of 100” — any way you slice it, you have nothing. The percentage formula You can use this simple percentage formula to find the share of a whole in terms of 100: Percentage = (Value/Total Value) x 100 As an example, suppose that in a group of 40 cats and dogs, 10 of the animals are dogs. What percentage is that? Solution: The number of dogs = 10 The total number of animals = 40 Using the percentage formula: Percentage of dogs = 10/40 x 100 = 25% How to calculate percent from decimals and fractions The number that you convert to find percentage can be given to you in two different formats: decimal and fraction. Decimal format is easier when you're learning how to calculate a percentage. Converting a decimal to a percentage is as simple as multiplying it by 100. To convert .87 to a percent, simply multiply .87 by 100. .87 × 100=87, which gives us 87 percent. Percent is often abbreviated with the % symbol. You can present your answer as 87% or 87 percent — either way is acceptable. If you are given a fraction, convert it to a percentage by dividing the top number by the bottom number. If you are given 13/100, you would divide 13 by 100. 13 ÷ 100 = .13 Then, follow the steps above for converting a decimal to a percent. .13 × 100 = 13, thus giving you 13%. The more difficult task comes when you need to know a percentage when you are given numbers that don’t fit so neatly into 100. Most of the time, you will be given a percentage of a specific number. For example, you may know that 40 percent of your paycheck will go to taxes and you want to find out how much money that is. How to calculate percentage of a specific number To get a percentage of a number, the process is the reverse of what you did earlier. First convert the percentage number to a decimal. Then, you divide your percentage by 100. So, 40 percent would be 40 divided by 100. 40 ÷ 100 = .40 Next, once you have the decimal version of your percentage, simply multiply it by the given number (in this case, the amount of your paycheck). If your paycheck is $750, you would multiply 750 by .40. 750 × .40 = 300 Your answer would be 300. You are paying $300 in taxes. Let’s try another example. You need to save 25 percent of your paycheck for the next 6 months to pay for an upcoming vacation. If your paycheck is $1,500, how much should you save? Start by converting 25 percent to a decimal. 25 ÷ 100 = .25 Now, multiply the decimal by the amount of your paycheck, or 1500. 1500 × .25 = 375 This means you need to save $375 from each paycheck. Dealing with percents greater than 100 percent 100 percent means “100 out of 100” — in other words, everything. So when I say I have 100 percent confidence in you, I mean that I have complete confidence in you. What about percentages more than 100 percent? Well, sometimes percentages like these don’t make sense. For example, you can’t spend more than 100 percent of your time playing basketball, no matter how much you love the sport; 100 percent is all the time you have, and there ain’t no more. But a lot of times, percentages larger than 100 percent are perfectly reasonable. For example, suppose I own a hot dog wagon and sell the following: 10 hot dogs in the morning 30 hot dogs in the afternoon The number of hot dogs I sell in the afternoon is 300% of the number I sold in the morning. It’s three times as many. Here’s another way of looking at this: I sell 20 more hot dogs in the afternoon than in the morning, so this is a 200% increase in the afternoon — 20 is twice as many as 10. Solving percent problems When you know the connection between percents and fractions, you can solve a lot of percent problems with a few simple tricks. Other problems, however, require a bit more work. In this section, I show you how to tell an easy percent problem from a tough one, and I give you the tools to solve all of them. A lot of percent problems turn out to be easy when you give them a little thought. In many cases, just remember the connection between percents and fractions, and you’re halfway home: Finding 100% of a number: Remember that 100% means the whole thing, so 100% of any number is simply the number itself: 100% of 5 is 5 100% of 91 is 91 100% of 732 is 732 Finding 50% of a number: Remember that 50% means half, so to find 50% of a number, just divide it by 2: 50% of 20 is 10 50% of 88 is 44 50% of 7 is (or or 3.5) Finding 25% of a number: Remember that 25% equals one-quarter, (1/4), so to find 25% of a number, divide it by 4: 25% of 40 = 10 25% of 88 = 22 25% of 15 = 15/4 = 3 3/4 = 3/75 Finding 20% of a number: Finding 20% of a number is handy if you like the service you’ve received in a restaurant, because a good tip is 20% of the check. Because 20% equals 1/5 , you can find 20% of a number by dividing it by 5. But I can show you an easier way: Remember that 20% is 2 times 10%, so to find 20% of a number, move the decimal point one place to the left and double the result: 20% of 80 = 8 x 2 = 16 20% of 300 = 30 x 2 = 60 20% of 41 = 4.1 x 2 = 8.2 Finding 10% of a number: Finding 10% of any number is the same as finding of that number. To do this, just move the decimal point one place to the left: 10% of 30 = 3 10% of 41 = 4.1 10% of 7 = 0.7 Finding 200%, 300%, and so on of a number: Working with percents that are multiples of 100 is easy. Just drop the two 0s and multiply by the number that’s left: 200% of 7 = 2 x 7 = 14 300% of 10 = 3 x 10 = 30 1,000% of 45 = 10 x 45 = 450 Turning the problem around Here’s a trick that makes certain tough-looking percent problems so easy that you can do them in your head. Simply move the percent sign from one number to the other and flip the order of the numbers. Suppose someone wants you to figure out the following: 88% of 50 Finding 88% of anything isn’t an activity anybody looks forward to. But an easy way of solving the problem is to switch it around: 88% of 50 = 50% of 88 This move is perfectly valid, and it makes the problem a lot easier. It works because the word of really means multiplication, and you can multiply either backward or forward and get the same answer. As I discuss in the preceding section, “Figuring out simple percent problems,” 50% of 88 is simply half of 88: 88% of 50 = 50% of 88 = 44 As another example, suppose you want to find 7% of 200 Again, finding 7% is tricky, but finding 200% is simple, so switch the problem around: 7% of 200 = 200% of 7 In the preceding section, I tell you that, to find 200% of any number, you just multiply that number by 2: 7% of 200 = 200% of 7 = 2 x 7 = 14

View ArticleArticle / Updated 05-10-2023

Hypothesis tests are used to test the validity of a claim that is made about a population. This claim that’s on trial, in essence, is called the null hypothesis (H0). The alternative hypothesis (Ha) is the one you would believe if the null hypothesis is concluded to be untrue. The evidence in the trial is your data and the statistics that go along with it. All hypothesis tests ultimately use a p-value to weigh the strength of the evidence (what the data are telling you about the population). The p-value is a number between 0 and 1 and interpreted in the following way: A small p-value (typically ≤ 0.05) indicates strong evidence against the null hypothesis, so you reject it. A large p-value (> 0.05) indicates weak evidence against the null hypothesis, so you fail to reject it. P-values very close to the cutoff (0.05) are considered to be marginal (could go either way). Always report the p-value so your readers can draw their own conclusions. How to find a p-value from a test statistic When you test a hypothesis about a population, you find a p-value and use your test statistic to decide whether to reject the null hypothesis. The following figure shows the locations of a test statistic and their corresponding conclusions. Note that if the alternative hypothesis is the less-than alternative, you reject H0 only if the test statistic falls in the left tail of the distribution (below –2). Similarly, if Ha is the greater-than alternative, you reject H0 only if the test statistic falls in the right tail (above 2). To find the p-value from your test statistic: Look up your test statistic on the appropriate distribution — in this case, on the standard normal (Z-) distribution in the p-value charts (called Z-tables) below. Find the probability that Z is beyond (more extreme than) your test statistic: If Ha contains a less-than alternative, find the probability that Z is less than your test statistic (that is, look up your test statistic on the Z-table and find its corresponding probability). This is the p-value. (Note: In this case, your test statistic is usually negative.) If Ha contains a greater-than alternative, find the probability that Z is greater than your test statistic (look up your test statistic on the Z-table, find its corresponding probability, and subtract it from one). The result is your p-value. (Note: In this case, your test statistic is usually positive.) If Ha contains a not-equal-to alternative, find the probability that Z is beyond your test statistic and double it. There are two cases: If your test statistic is negative, first find the probability that Z is less than your test statistic (look up your test statistic on the Z-table and find its corresponding probability). Then double this probability to get the p-value. If your test statistic is positive, first find the probability that Z is greater than your test statistic (look up your test statistic on the Z-table, find its corresponding probability, and subtract it from one). Then double this result to get the p-value. You might be wondering why you double the probabilities if your Ha contains a non-equal-to alternative? Think of the not-equal-to alternative as the combination of the greater-than alternative and the less-than alternative. If you’ve got a positive test statistic, its p-value only accounts for the greater-than portion of the not-equal-to alternative; double it to account for the less-than portion. (The doubling of one p-value is possible because the Z-distribution is symmetric.) Similarly, if you’ve got a negative test statistic, its p-value only accounts for the less-than portion of the not-equal-to alternative; double it to also account for the greater-than portion. For example, when testing Ho: p = 0.25 versus Ha: p < 0.25, the p-value turns out to be 0.1056. This is because the test statistic was –1.25, and when you look this number up on the Z-table (in the appendix) you find a probability of 0.1056 of being less than this value. If you had been testing the two-sided alternative, Ha: p ≠ 0.25, the p-value would be 2 * 0.1056, or 0.2112. If the results are likely to have occurred under the claim, then you fail to reject Ho (like a jury decides not guilty). If the results are unlikely to have occurred under the claim, then you reject Ho (like a jury decides guilty). The cutoff point between rejecting Ho and failing to reject Ho is another whole can of worms that I dissect in the next section (no pun intended). Making Conclusions To draw conclusions about Ho (reject or fail to reject) based on a p-value, you need to set a predetermined cutoff point where only those p-values less than or equal to the cutoff will result in rejecting Ho. This cutoff point is called the alpha level (α), or significance level for the test. While 0.05 is a very popular cutoff value for rejecting Ho, cutoff points and resulting decisions can vary — some people use stricter cutoffs, such as 0.01, requiring more evidence before rejecting Ho, and others may have less strict cutoffs, such as 0.10, requiring less evidence. If Ho is rejected (that is, the p-value is less than or equal to the predetermined significance level), the researcher can say they've found a statistically significant result. A result is statistically significant if it’s too rare to have occurred by chance assuming Ho is true. If you get a statistically significant result, you have enough evidence to reject the claim, Ho, and conclude that something different or new is in effect (that is, Ha). The significance level can be thought of as the highest possible p-value that would reject Ho and declare the results statistically significant. Following are the general rules for making a decision about Ho based on a p-value: If the p-value is less than or equal to your significance level, then it meets your requirements for having enough evidence against Ho; you reject Ho. If the p-value is greater than your significance level, your data failed to show evidence beyond a reasonable doubt; you fail to reject Ho. However, if you plan to make decisions about Ho by comparing the p-value to your significance level, you must decide on your significance level ahead of time. It wouldn’t be fair to change your cutoff point after you’ve got a sneak peak at what’s happening in the data. You may be wondering whether it’s okay to say “Accept Ho” instead of “Fail to reject Ho.” The answer is a big no. In a hypothesis test, you are not trying to show whether or not Ho is true (which accept implies) — indeed, if you knew whether Ho was true, you wouldn’t be doing the hypothesis test in the first place. You’re trying to show whether you have enough evidence to say Ho is false, based on your data. Either you have enough evidence to say it’s false (in which case you reject Ho) or you don’t have enough evidence to say it’s false (in which case you fail to reject Ho). Setting boundaries for rejecting Ho These guidelines help you make a decision (reject or fail to reject Ho) based on a p-value when your significance level is 0.05: If the p-value is less than 0.01 (very small), the results are considered highly statistically significant — reject Ho. If the p-value is between 0.05 and 0.01 (but not super-close to 0.05), the results are considered statistically significant — reject Ho. If the p-value is really close to 0.05 (like 0.051 or 0.049), the results should be considered marginally significant — the decision could go either way. If the p-value is greater than (but not super-close to) 0.05, the results are considered non-significant — you fail to reject Ho. When you hear a researcher say their results are found to be statistically significant, look for the p-value and make your own decision; the researcher’s predetermined significance level may be different from yours. If the p-value isn’t stated, ask for it. Testing varicose veins As an example of making a decision on whether to reject an Ho, suppose there's a claim that 25 percent of all women in the U.S. have varicose veins, and the p-value was found to be 0.1056. This p-value is fairly large and indicates very weak evidence against Ho by almost anyone’s standards because it’s greater than 0.05 and even slightly greater than 0.10 (considered to be a very large significance level). In this case you fail to reject Ho. You didn’t have enough evidence to say the proportion of women with varicose veins is less than 0.25 (your alternative hypothesis). This isn’t declared to be a statistically significant result. But say your p-value had been something like 0.026. A reader with a personal cutoff point of 0.05 would reject Ho in this case because the p-value (of 0.026) is less than 0.05. The reader's conclusion would be that the proportion of women with varicose veins isn’t equal to 0.25; according to Ha in this case, you conclude it’s less than 0.25, and the results are statistically significant. However, a reader whose significance level is 0.01 wouldn’t have enough evidence (based on your sample) to reject Ho because the p-value of 0.026 is greater than 0.01. These results wouldn’t be statistically significant. Finally, if the p-value turned out to be 0.049 and your significance level is 0.05, you can go by the book and say because it’s less than 0.05 you reject Ho, but you really should say your results are marginal, and let the reader decide.

View ArticleArticle / Updated 05-09-2023

Dropping demonstrative adjectives into your Spanish vocabulary will help you express exactly what or whom you’re seeking. But first, you need to understand what demonstrative adjectives stand for and how they translate in Spanish. Then you’ll be ready to absorb the basics of their usage. Demonstrative adjectives indicate or point out the person, place, or thing to which a speaker is referring. For instance, “this shirt” or “that pair of pants.” They precede and agree in number and gender with the nouns they modify. In Spanish, you select the demonstrative adjective according to the distance of the noun from the speaker. The following table presents demonstrative adjectives and addresses this distance issue. Spanish Demonstrative Adjectives Number Masculine Feminine Meaning Distance Singular/Plural este/estos esta/estas this/these Near to or directly concerned with speaker Singular/Plural ese/esos esa/esas that/those Not particularly near to or directly concerned with speaker Singular/Plural aquel/aquellos aquella/aquellas that/those Far from and not directly concerned with speaker The following list shows these demonstrative adjectives in action: Estos pantalones son cortos y esta camisa es larga. (These pants are short and this shirt is large.) Tengo que hablar con esa muchacha y esos muchachos ahí. (I have to speak to that girl and those boys there.) Aquellos países son grandes y aquellas ciudades son pequeñas. (Those countries are large and those cities are small.) Here’s what you need to know about demonstrative adjectives in Spanish: You use them before each noun: este abogado y ese cliente (this lawyer and that client) You can use adverbs to reinforce location: esta casa aquí (this house here) esas casas ahí (those houses there) aquella casa allá (that house over there)

View ArticleArticle / Updated 05-09-2023

Demonstrative pronouns can make your Spanish flow more naturally in both writing and conversation. So how exactly can you go about forming sentences with demonstrative pronouns? First, you need to understand what they stand for and how they translate in Spanish. Then you’ll be ready to absorb the basics of their usage. Demonstrative pronouns, which replace demonstrative adjectives and their nouns, express this (one), that (one), these (ones), or those (ones). The only difference between a demonstrative adjective and a demonstrative pronoun in terms of writing is the addition of an accent to the pronoun, as you can see in the following table. Spanish Demonstrative Pronouns Number Masculine Feminine Meaning Distance Singular/Plural éste/éstos ésta/éstas this (one)/these (ones) Near to or directly concerned with speaker Singular/Plural ése/ésos ésa/ésas that (one)/those (ones) Not particularly near to or directly concerned with speaker Singular/Plural aquél/aquéllos aquélla/aquéllas that (one)/those (ones) Far from and not directly concerned with speaker The following list shows some examples of these demonstrative pronouns in action: Mire éstos y ésta también. (Look at these and this one, too.) Quiero ése y ésas. (I want that and those.) Aquél es viejo y aquélla es moderno. (That one is old and that one is modern.) Here’s what you need to know about demonstrative pronouns in Spanish: They agree in number and gender with the nouns they replace: Me gusta este coche y ésos. (I like this car and those.) You use a form of aquél to express the former and a form of éste to express the latter: Patricia es la hermana de Francisco; éste es rubio y aquélla es morena. (Patricia is the sister of Francisco; Francisco [the latter] is blond and Patricia [the former] is brunette.)

View ArticleArticle / Updated 05-09-2023

When speaking Spanish, the pronoun you use depends upon the person you’re speaking to and the person you’re speaking about. And, just as in English, you change pronouns according to person — I, you, he or she and we, you, they. The following table shows all the Spanish subject pronouns: Person Singular Plural 1st Person yo (I) nosotros/as (we [male or mixed group/female]) 2nd Person tœ (you [informal]); Ud. (you [formal]) vosotros/as (you [informal; male or mixed group/female]); Uds. (you [formal]) 3rd Person Žl (he); ella (she) ellos/as (they [male or mixed group/female])

View ArticleCheat Sheet / Updated 05-08-2023

Why is Neuroscience important? The most complex structure in the world is the 3-pound mass of cells within your skull called the brain. The brain consists of about 100 billion neurons, which is about the same number as all the stars in our Milky Way galaxy and the number of galaxies in the known universe. It also contains about a trillion glial cells, which contribute to the proper function of neurons. Like any complex machine, the brain contains a lot of parts, each of which has subparts, which themselves have subparts, all the way down to the “nuts and bolts” — the neurons and glia. In this Cheat Sheet, you find information on the key parts of the brain and the role and function of the cells that make up the nervous system.

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