Question

You have gathered data on litter size for bonnethead sharks from two different latitudes (a northern and a southern site). The columns represent the number of pups produced by each female shark that you sampled. You are interested in whether or not a difference exists between latitudes. Set up and test an appropriate statistical hypothesis that you would use to try to answer this question. Calculate 95% confidence intervals for each group. Do either of these intervals contain a mean litter size of 45 pups?

How would I set up a hypothesis for this and how do you calculate confidence intervals for groups?

Answer 1

To test for difference in two group of sharks we use t-test for difference of means .The test is carried out as follows:

We calculate the mean and sample s.d for the two latitude sharks.

Suppose that we have the following hypothetical data:

Latitude 1	Latitude 2
mean1=50	mean2=41
sample S.D(s1)=4.5	sample S.D(s2)=3.2
n1=15	n2=17

Now we test the hypothesis whether there is a difference between the two means.

The same can be done when data is provided.

Now to construct confidence interval for the hypothetical data assumed:

Since 45 is not contained in the interval therefore the interval does not contain 45.

Similar interval can be calculated for the latitude 2 .

Please note: The calculations are done on hypothetical data. If you need exact answers please update the question with data.