Question

In a study on the effects stress on behaviour in rats, 78 rats were randomly assigned to either a stressful environment or a control (non-stressful) environment.
After 21 days, the change in weight (in grams) was determined for each rat.

The following table summarises the data on weight gain:

	n	sample mean	sample standard deviation
Stress	23	21.08	13.49
No stress	55	28.14	15.39

1.2 (1 mark)

Calculate the value of the t-statistic to three decimal places

1.3 (.6 marks)

Using the simple method, how many degrees of freedom df does this t-statistic have? df =

1.4 (1 mark)

Calculate the p-value to three decimal places. P-value ≈

1.6 (2 marks)

Now we require you to calculate a (1 − α) ×100 = 99% confidence interval for the true mean difference between μ1 and μ2. 1.6.1 (1 mark) In order to do that, what, to three decimal places, is the value of the t-statistic t* that you should be using in the expression for the confidence interval? t* ≈

1.6.2 (1 mark)

Enter the confidence interval (lo, hi), where lo and hi are the lower and upper limits, respectively, to three decimal places. (lo, hi) =

1.7 (.2 marks)

Is the result from the hypothesis test consistent with the confidence interval?

Answer 1