# chapter 8 Confident level

#### Lucyzzz

A sample of 18 small bags of the same brand of candies was selected. Assume that the population distribution of bag weights is normal. The weight of each bag was then recorded. The mean weight was 3 ounces with a standard deviation of 0.14 ounces. The population standard deviation is known to be 0.1 ounce.

NOTE: If you are using a Student's t-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

x =

σ =

sx =

Could someone explain to me as how which one is σ and which is sx?

#### Debsta

MHF Helper
sigma represents the population standard deviation.
s represents the sample standard deviation.

topsquark

#### Lucyzzz

I already tried and the computer say is wrong

#### Debsta

MHF Helper
Have you given the question EXACTLY as worded?

#### Lucyzzz

Ok for the Sx I divided 3/18 is that correct? And I used the z-interval σ= .01, mean=3 n=18 with c level of .98 to State the confidence interval, and I obtain 2.995, 3.006, and an error bound of .006. But still, mark wrong. Maybe I am using the wrong interval?

#### Debsta

MHF Helper
Are you using sx as the symbol for the standard error?
If so, sx is not 3/18,

#### Lucyzzz

No sx is like you said before. But I already tried 0.14 and they marked me wrong

#### Debsta

MHF Helper
Please show how you calculated the CI.

#### Lucyzzz

I used the calculator one question for the σ to calculate z interval I need use .14 or .01?

#### Debsta

MHF Helper
I used the calculator one question for the σ to calculate z interval I need use .14 or .01?
What did you actually put into your calculator??
Can you please quote the whole question as given to you?