00:01
For this question, we are asked to find a 95 % confidence interval for the difference of the means in exercise 6.
00:09
Recall in exercise 6, we had samples for hard -body and soft -body vacuum cleaners, and we were interested in the weights of these vacuum cleaners, specifically the mean weights.
00:23
So in this table, i've summarized the samples in terms of the sample size, the sample means, and the sample standard deviations.
00:30
And the way i did that was by pasting the data from the question into excel in these two columns here, and then using the average function in excel to find the averages, and the sample standard deviation function in excel to find the sample standard deviations.
00:50
And so a confidence interval for the difference in average weights is given by this formula.
01:17
So if we first calculate our critical value, we are going to use a degrees of freedom that is the smaller of the samples in size minus 1, so that gives us 5.
01:33
And the confidence level is 95%, so alpha is equal to 0 .05.
01:39
And so we can look that up in the table...