Divide the fraction by 12. This is because we need to split the sugar between 12 brownies, and to split something means to divide it. Use the switch, flip and multiply method.
I inserted an image on how to use this method.
Anyway, to use this method, we need 2 fractions, so instead of 12, we have to use .
The 98% confidence interval for the mean repair cost for the dryers is (83.4161, 103.3039).
Step-by-step explanation:
We have a small sample size n = 25, and s = 19.95. The confidence interval is given by where is the th quantile of the t distribution with n - 1 = 25 - 1 = 24 degrees of freedom. As we want the 98% confidence interval, we have that and the confidence interval is where is the 1st quantile of the t distribution with 24 df, i.e., . Then, we have and the 98% confidence interval is given by (83.4161, 103.3039).