1. ## 2 SPSS questions

I've got these SPSS results refering to a study where horses and camels were injected with tripelenamine.

I have 2 questions:

1) How do I calculate the 95% confidence/trust interval for comparing the variability of the percentage of drugs in horses and camels' blood?

2) For a level of significance of 5%, is there sufficient statistical evidence to say
that, on average, the percentage of drugs in blood is equal in horses and camels after administration of tripelenamine?

I have no idea how to solve the first question, as for the second, isn't the answer already on the yellow boxes? Sorry for the dumb questions

2. ## Re: 2 SPSS questions

Typically, one will use Levene's Test to test the equality of variances. A significance above 0.05 in such a test would suggest equal population variances between the horse group and the camel group. You can also look at summary statistics and see if the variances of the two groups are roughly the same. I do not see anything in your output that allows you to directly compute a 95% confidence interval for variability.

If you can assume equal variances (ideal), then use the equal variance t-test results to draw conclusions about about population means. Remember that $F=t^2$.

You can answer the second part of your question because your output gives results for both equal variances and separate variances (and both tests lead you to the same conclusion). Since the significance for both the equal and separate variance conditional means tests are very low, there appears to be difference in percentage of drugs in horse and camel blood.

Good luck!