## The Difference between Two Means

This section covers how to test for differences between means from two separate groups of subjects and gives an example of opinions on animal research. The detailed testing procedure is carried out using the standard steps in hypothesis testing.

### Questions

Question 1 out of 9.
The graphs show a violation of the assumption of (check all that apply) • normality
• homogeneity of variance

Question 2 out of 9.
The graphs show a violation of the assumption of (check all that apply) • normality
• homogeneity of variance

Question 3 out of 9.

The graphs show a violation of the assumption of (check all that apply) • normality
• homogeneity of variance

Question 4 out of 9.

In the formula for $t$, the "statistic" is

• the null hypothesis.
• the mean of all numbers.
• the difference between sample means.
• the significance level.

Question 5 out of 9.

In the formula for $t$, the "hypothesized value" is

• what you expect the $t$ to be.
• the difference between population means.
• the significance level.

Question 6 out of 9.

If the null hypothesis is that two population means are equal, then the hypothesized value is

• 0.
• the population mean.

Question 7 out of 9.

The denominator in the $t$ test formula is

• the estimated standard error of the mean.
• the estimated standard error of the difference between means.
• MSE/2

Question 8 out of 9.
If there are 4 scores per group and the $t$ value is 2.34, what is the $p$ value for a two-tailed test (to 3 decimal places)?

___________

Question 9 out of 9.
What is the t for an independent-groups $t$ test for these data?

___________

  G 1	  G 2
46	 28
59	 37
53	 40
35	 34
43	 29
28	 46
59	 26
51	 41