The hourly rate of substitute teachers for 12 local school districts is given below. Assuming that the data are normally distributed, use a TI-83, or TI-84 calculator to find the 90% confidence interval for the mean hourly rate of substitute teachers in the region.20 13 21 18 19 2219 15 12 12 18 21

Step-by-step explanation:

Data given

20 13 21 18 19 22 19 15 12 12 18 21

We can calculate the sample mean and deviation with the following formulas:

And we got:

represent the sample mean

population mean (variable of interest)

s=3.61 represent the sample standard deviation

n=12 represent the sample size  

Confidence interval

The confidence interval for the mean is given by the following formula:

  (1)

The degrees of freedom are given by:

Since the Confidence is 0.90 or 90%, the significance is and , the critical value would be given by

Now we have everything in order to replace into formula (1):

21.4 i did it already for s1

step-by-step explanation:

my answer is$ 12

step-by-step explanation:

because 15 -2=12