To compute the mean, you simply have to sum all the elments in the data set and the divide the sum by the number of elements:
To compute the variance, we first need to compute the distance of each element from the mean. To do so, we build a "parallel" dataset, given by the difference of every value and the mean:
Now we need those difference squared:
The variance is the mean of this new vector, so
Finally, the standard deviation is simply the square root of the variance, so you have
Answer:
The value of the test statistic is z = -0.877.
Step-by-step explanation:
Testing the difference in mean time spent on housework between husbands and wives.
At the null hypothesis, we test if there is no difference, that is, the subtraction of the means is 0:
At the alternate hypothesis, we test if there is a difference, that is, the subtraction of the means is different from 0.
The test statistic is:
In which X is the sample mean, is the value tested at the null hypothesis, and s is the standard error.
0 is tested at the null hypothesis:
This means that
For the wives the mean was 7 hours/week and for the husbands the mean was 4.5 hours/week. The standard deviation of the differences in time spent on house work was 2.85.
This means that
What is the value of the test statistic for testing the difference in mean time spent on housework between husbands and wives?
The value of the test statistic is z = -0.877.