Lecture 10- Hypothesis Testing 3

Question 1

What is a t-test used for?

Answer 1

Parametric procedure used to test the null hypothesis for a single-sample experiment when the standard deviation of the population
must be estimated

Question 2

What is the most important thing about t-tests to do with sample size?

Answer 2

It works for small samples where the standard normal does not accurately represent the sample

Question 3

What do the different t- distributions depending on?

Answer 3

Sample size or n-1 (degrees of freedom : df)

Question 4

What is the definition of degrees of freedom?

Answer 4

How many scores in the sample are free to vary – generally all scores
except the last one hence n-1

Question 5

How is a T- distribution different from a normal distribution?

Answer 5

Tails of T distribution are fatter (don’t go right don’t go to zero as fast)= variability is greater

Question 6

What are the three assumptions of a single tailed t-test?

Answer 6

1. The random sample comprises interval or ratio scores.
2. The distribution of individual scores is normal.
3. The standard error of the mean is estimated using the sx computed
   from the sample

Question 7

What are the four steps in carrying out a t-test to determine whether or not to reject the null hypothesis?

Answer 7

1. Calculate the observed t using the estimated standard error of the mean
2. Determine the df
3. Look up the critical t in the t-Table with the appropriate df (and alpha)
4. If observed t is greater than or equal to the tabled value then reject the null

Question 8

In what case do you use a 2 sample t-test?

Answer 8

When have two groups and want to compare if they are different or not

Question 9

How do you carry out a 2 sample t-test?

Answer 9

We compare the difference between two sample means taking into account the sampling error by calculating the estimated standard error of the difference between the sample means and use the student t-test and distribution.

Question 10

In a two sample t-test what does our estimate of the standard error of the means differ according to?

Answer 10

Differs according to whether the two sets of scores are from the same (within subjects) or different (between subjects) groups.