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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…]

Generalizing Statistical Results to the Entire Population
Making conclusions about a much broader population than your sample actually represents is one of the biggest nono's in statistics. This kind of problem is called [more…]
Found in: Statistics 
Handling Statistical Hypothesis Tests
You use hypothesis tests to challenge whether some claim about a population is true (for example, a claim that 40 percent of Americans own a cellphone). To test a statistical hypothesis, you take a sample [more…]
Found in: Statistics 
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 
Understanding Formulas for Common Statistics
After data has been collected, the first step in analyzing it is to crunch out some descriptive statistics to get a feeling for the data. For example: [more…]
Found in: Statistics 
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 
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 
How to Identify Statistical Bias
Bias is a word you hear all the time in statistics, and you probably know that it means something bad. But what really constitutes bias? Bias is systematic favoritism that is present in the data collection [more…]
Found in: Statistics Basics