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143 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…]

Computer Output for Statistics II
If you’re taking Statistics II, you’re likely to face questions on computer output for multiple regression and ANOVA. Professors like to give output on exams and ask you to interpret it. Sometimes they [more…]
Found in: Statistics 
How to Find Percentiles for a tDistribution
When you want to find percentiles for a tdistribution, you can use the ttable. A percentile is a number on a statistical distribution whose lessthan probability is the given percentage; for example, [more…]
Found in: Binomial, Normal & tDistributions 
How Sample Size Affects Standard Error
The size (n) of a statistical sample affects the standard error for that sample. Because n is in the denominator of the standard error formula, the standard error decreases as [more…]
Found in: Binomial, Normal & tDistributions 
Using Linear Regression to Predict an Outcome
Statistical researchers often use a linear relationship to predict the (average) numerical value of Y for a given value of X using a straight line (called the [more…]
Found in: Statistical Data 
How to Find the Interquartile Range for a Statistical Sample
To obtain a measure of variation based on the fivenumber summary of a statistical sample, you can find what's called the interquartile range, or IQR.
The purpose of the fivenumber summary is to give descriptive [more…]
Found in: Calculating & Graphing Statistical Data 
How a Pie Chart Reflects Categorical Data in a Statistical Data Set
A pie chart takes categorical data from a statistical sample and breaks them down by group, showing the percentage of individuals that fall into each group. Because a pie chart takes on the shape of a [more…]
Found in: Calculating & Graphing Statistical Data 
What the Distribution Tells You about a Statistical Data Set
The distribution of a statistical data set (or a population) is a listing or function showing all the possible values (or intervals) of the data and how often they occur. When a distribution of categorical [more…]
Found in: Statistics Basics 
Avoid Drawing the Wrong Conclusions from Statistical Data
Statistical formulas don’t know whether they are being used properly, and they don’t warn you when your results are incorrect. In order to draw the appropriate conclusions, it’s up to you to avoid overstating [more…]
Found in: Statistics Basics 
How to Interpret the Margin of Error in Statistics
You’ve probably heard or seen results like this: “This statistical survey had a margin of error of plus or minus 3 percentage points.” What does this mean? Most surveys are based on information collected [more…]
Found in: Statistics Basics 
How to Find RightTail Values and Confidence Intervals Using the tTable
You can use a ttable to find righttail probabilities and pvalues for hypothesis tests and to find t*values (critical values) for a confidence interval involving [more…]
Found in: Binomial, Normal & tDistributions 
How to Identify the Notation for the Mean and Variance of a Discrete Random Variable
Two of the most important terms in statistics are mean and variance, and so you need to be able to identify their notations when working with discrete random variables. [more…]
Found in: Binomial, Normal & tDistributions 
How to Tell a ZDistribution from a tDistribution
Although the normal (Z) distribution and tdistribution are similar, they look different from each other and are used for different statistical purposes. The normal distribution is that wellknown bellshaped [more…]
Found in: Binomial, Normal & tDistributions 
How zValues Are Used in Statistics
If a statistical data set has a normal distribution, it is customary to standardize all the data to obtain standard scores known as zvalues or zscores. The distribution of [more…]
Found in: Statistics Basics 
How to Find Probabilities for a Sample Mean
In statistics, you can easily find probabilities for a sample mean if it has a normal distribution. Even if it doesn’t have a normal distribution, or the distribution is not known, you can find probabilities [more…]
Found in: Binomial, Normal & tDistributions 
How to Interpret a Scatterplot
Scatterplots are useful for interpreting trends in statistical data. Each observation (or point) in a scatterplot has two coordinates; the first corresponds to the first piece of data in the pair [more…]
Found in: Statistical Data 
How to Determine a pValue When Testing a Null Hypothesis
When you test a hypothesis about a population, you can use your test statistic to decide whether to reject the null hypothesis, H_{0}. You make this decision by coming up with a number, called a [more…]
Found in: Variance & Margin of Error 
Statistics For Dummies Cheat Sheet
Whether you’re studying for an exam or just want to make sense of data around you every day, knowing how and when to use data analysis techniques and formulas of statistics will help. Being able to make [more…]
Found in: Statistics 
Checking Out Statistical Confidence Interval Critical Values
Critical values (z*values) are an important component of confidence intervals (the statistical technique for estimating population parameters). The z* [more…]
Found in: Statistics 
How to Calculate a Regression Line
In statistics, you can calculate a regression line for two variables if their scatterplot shows a linear pattern and the correlation between the variables is very strong [more…]
Found in: Statistical Data 
Working with Statistical TwoWay Tables
To explore the links between two categorical variables, you first need to organize the data that’s been collected, and a table is a great way to do that. A [more…]
Found in: Statistical Data 
Applying the Empirical Rule (689599.7) to a Statistical Data Set
The Empirical Rule (689599.7) says that if the population of a statistical data set has a normal distribution (where the data are in the shape of a bell curve) with population mean [more…]
Found in: Calculating & Graphing Statistical Data 
Avoid Bias with Random Statistical Samples
How do you select a statistical sample in a way that avoids bias? The key word is random. A random sample is a sample selected by equal opportunity; that is, every possible sample of the same size as yours [more…]
Found in: Statistics Basics 
Describing Your Statistical Data with Numbers
After collecting good statistical data, you can summarize it with descriptive statistics. These are numbers that describe a data set in terms of its important features: [more…]
Found in: Statistical Data 
How to Identify Skew and Symmetry in a Statistical Histogram
Sometimes the mean versus median debate can get quite interesting. Especially when you look at the skewness and symmetry of your statistical data in a histogram. [more…]
Found in: Calculating & Graphing Statistical Data