Ch 10: Estimating Means with Confidence

standard error of x

standard error of x

Replacing the SD with the SE requires the use of the ____ rather than the normal distribution.

 t distribution

The number of degrees of freedom is equal to

n-1

A sample meets the condition for being Random if:

the data come from a random sample from the population of interest

A sample meets the condition for being Independent if:

10% condition is satisfied when sampling without replacement

A sample meets the condition for being approximately Normal if:

1. We are told the population is Normally distributed, or

2. The sample size is large enough, by the Central Limit Theorem (n≥30), or

3. Graph/sketch the sample data to assess the Normality; look for large skewness or outliers

equation for one-sample t interval for μ

(use table B for t* values, and df=n-1)

Margin of error ____ when sample size increases

decreases

Margin of error _____ when confidence level increases

increases

conditions to fulfill for confidence intervals for μ1-μ2

1. Independent random samples, or from two groups in a randomized experiment

2. 10% condition when sampling without replacement for both n1 and n2

3. For each sample, follow same rules as above (for 1 sample)

name of procedure for μ1-μ2

two sample t interval for a difference between two means

conservative method for calculating degrees of freedom with two samples

take the smaller of n₁-1 and n₂-1

formula for a two sample t interval for a difference in means

______ result from recording two values of the same quantitative variable for each individual or for each pair of similar individuals

paired data

name of the procedure for paired data

one sample t interval for a mean difference OR paired t interval for a mean difference