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131 results for "Deborah J. Rumsey"

Statistics Tables for Reference
Several commonly used tables in statistics include the Ztable, the ttable, the binomial table, and a table of z*values for selected confidence levels. Excerpted from [more…]

Choosing a Confidence Level for a Population Sample
In statistics, every confidence interval (and every margin of error, for that matter) has a percentage associated with it, called a confidence level. This percentage represents how confident you are that [more…]
Found in: Variance & Margin of Error 
How the Central Limit Theorem Is Used in Statistics
The normal distribution is used to help measure the accuracy of many statistics, including the sample mean, using an important result called the Central Limit Theorem. [more…]
Found in: Statistics Basics 
How Treatment Groups, Control Groups, Placebos, and Blind Experiments Are Used in Statistics
Statistical studies often involve several kinds of experiments: treatment groups, control groups, placebos, and blind and doubleblind tests. An experiment [more…]
Found in: Statistics Basics 
How to Determine the Confidence Interval for a Population Proportion
You can find the confidence interval (CI) for a population proportion to show the statistical probability that a characteristic is likely to occur within the population. [more…]
Found in: Variance & Margin of Error 
How Population Standard Deviation Affects Standard Error
In statistics, the standard deviation in a population affects the standard error for that population. Standard deviation measures the amount of variation in a population. In the standard error formula [more…]
Found in: Binomial, Normal & tDistributions 
How to Find the Sampling Distribution of a Sample Proportion
If you use a large enough statistical sample size, you can apply the Central Limit Theorem (CLT) to a sample proportion for categorical data to find its sampling distribution. The [more…]
Found in: Binomial, Normal & tDistributions 
Types of Statistical Data: Numerical, Categorical, and Ordinal
When working with statistics, it’s important to recognize the different types of data: numerical (discrete and continuous), categorical, and ordinal. Data [more…]
Found in: Statistical Data 
How to Compare Two Population Proportions
For statistical purposes, you can compare two populations or groups when the variable is categorical (for example, smoker/nonsmoker, Democrat/Republican, support/oppose an opinion, and so on) and you’re [more…]
Found in: Statistical Data 
How to Test for an Average Difference Using the Paired tTest
You can test for an average difference using the paired ttest when the variable is numerical (for example, income, cholesterol level, or miles per gallon) and the individuals in the statistical sample [more…]
Found in: Statistical Data 
How to Calculate Standard Deviation in a Statistical Data Set
By far the most common measure of variation for numerical data in statistics is the standard deviation. The standard deviation measures how concentrated the data are around the mean; the more concentrated [more…]
Found in: Calculating & Graphing Statistical Data 
How to Find a Percentile for a Normal Distribution
A popular normal distribution problem involves finding percentiles for X. That is, you are given the percentage or statistical probability of being at or below a certain [more…]
Found in: Binomial, Normal & tDistributions 
How to Find the Mean, Variance, and Standard Deviation of a Binomial Distribution
Because the binomial distribution is so commonly used, statisticians went ahead and did all the grunt work to figure out nice, easy formulas for finding its mean, variance, and standard deviation. The [more…]
Found in: Binomial, Normal & tDistributions 
How to Indicate Possible Outcomes for a Discrete Random Variable
A discrete random variable X can take on a certain set of possible outcomes, and each of those outcomes has a certain statistical probability of occurring. The notation used for any specific outcome is [more…]
Found in: Binomial, Normal & tDistributions 
Probability Study Tips
If you're going to take a probability exam, you can better your chances of acing the test by studying the following topics. They have a high probability of being on the exam. [more…]
Found in: Probability 
Figuring Out What Probability Means
Probabilities come in many different disguises. Some of the terms people use for probability are chance, likelihood, odds, percentage, and proportion. But the basic definition of [more…]
Found in: Math 
Using Probability When Hitting the Slot Machines
Remember the movie National Lampoon's Vegas Vacation, when gambling fever consumes Chevy Chase's character, Clark W. Griswold? He goes on a losing streak to beat all losing streaks while his son, Rusty [more…]
Found in: Math 
Creating a Confidence Interval for the Difference of Two Means with Known Standard Deviations
If you know the standard deviations for two population samples, then you can find a confidence interval (CI) for the difference between their means, or averages. The goal of many statistical surveys and [more…]
Found in: Variance & Margin of Error 
How to Create a Confidence Interval for the Difference of Two Means with Unknown Standard Deviations and/or Small Sample Sizes
You can find a confidence interval (CI) for the difference between the means, or averages, of two population samples, even if the population standard deviations are unknown and/or the sample sizes are [more…]
Found in: Variance & Margin of Error 
How to Test a Hypothesis for One Population Mean
You can use a hypothesis test to examine or challenge a statistical claim about a population mean if the variable is numerical (for example, age, income, time, and so on) and only one population or group [more…]
Found in: Statistical Data 
Simplifying Excess Statistical Data in a Time Chart
If a time chart includes too much statistical data, the result can be so complex that it makes it impossible to interpret the data. By reducing the amount of data, it is easier to see patterns emerge from [more…]
Found in: Calculating & Graphing Statistical Data 
How Histograms Can Misrepresent Statistical Data
There are no hard and fast rules for how to create a histogram based on a set of statistical data; the person making the graph gets to choose the groupings on the [more…]
Found in: Calculating & Graphing Statistical Data 
How a Sampling Distribution Is Affected When the Distribution Is Not Normal
In statistics, if a population X has any distribution that is not normal, or if its distribution is unknown, you can’t automatically say the distribution of the sample means [more…]
Found in: Binomial, Normal & tDistributions 
How to Identify a Sampling Distribution
In statistics, a sampling distribution is based on sample averages rather than individual outcomes. This makes it different from a distribution. Here’s why: A [more…]
Found in: Binomial, Normal & tDistributions 
Why Standard Deviation Is an Important Statistic
The standard deviation is a commonly used statistic, but it doesn’t often get the attention it deserves. Although the mean and median are out there in common sight in the everyday media, you rarely see [more…]
Found in: Statistics Basics