Question 1

You take a random sample of 16 from a normal population of mean 30 and population standard deviation of 8. Find the 90% confidence interval for the population mean.

Since pop mean is known i dont need t score, right?

also, do I have to divide the sd by the srt of n even though i am given the pop sd?

the answer I got was, 30 plus/minus 1.645(8/srt2)

Question 2

A purchaser of light bulbs wants to test the hypothesis that the average lifetime is more than 100 hours. She takes a random sample of 16 and gets a sample mean of 96 with a sample standard deviation of 8 hours.

a) Should she accept the hypothesis that they last more than 100 hours at the 95% level of confidence?

b) What about at the 99% level of confidence.\?

I dont know what to do with this problem. Its a small sample size but not sure what t score to use or what to do with it :P

i can get the t score of .05 which is 1.753 and i have a formula for t score thats u - x/(s/sqrt n)

i could use a lot of help with 2. im not asking for the answer, just a little info on how to do it.

Thank you.