Day 11

Question 1

Hypothesis testing continued

Answer 1

To help determine if a specific treatment has an effect . If a sample from a sub-group within a population is significant. Z scores assume you already know a certain amount of data.

Question 2

T-statistics

Answer 2

Used when population is unknown so the standard error of the mean cannot be calulateD. An estimated standard error of the mean is calculated using the sample standard deviation instead. SM= square root of (sample variance dividing sample n)

Question 3

T vs. D distribution

Answer 3

Standard error of the mean (SE) will be the same for every sample of a particular size because it uses the pop standard deviation. Because the t statistic uses the sample narrowed to estimate the standard error, the estimated standard error (sm) will be different for different samples.

Question 4

Two general situations where a single sample t - test is used

Answer 4

To determine whether or not a treatment causes a change in a known population mean orWhen there is a hypothesized value for an unknown.

Question 5

Cohens D

Answer 5

Cohens D is a measure of effect size. Mean difference/ SD= cohens D.

Question 6

Assumption of a t-test

Answer 6

Independent observation pop is normally distributed. However that t statistic is a robust statistic; violation of the second criterion have little effect, especially when the sample size is relatively large.

Question 7

What is considered a large/ trustworthy statistic?

Answer 7

Once statistic is above 30 it is considered trustworthy

Question 8

Research designs

Answer 8

Between subjects or independent sample design with subjects or repeated measures design.

Question 9

When comparing two or more samples

Answer 9

The more variable the samples, the harder it is to detect a treatment difference. To decide whether two means from one to another.

Question 10

Assumptions of independent sample T-test

Answer 10

Observation in each sample are independent, population from which both samples are selected are nominal. Both pop. have equal variables. Violations of the third assumptions is a problem.

Question 11

Single sample t test vs. independent sample t test.

Answer 11

One set of scores compared to a known or predicted pop mean vs. two sets of scores (separate groups) (experimental and control) compare to one another.

Question 12

Calculating effect size

Answer 12

We need the pooled SD to calculate Cohens D.