confidence intervals

this is one of my questions on my homework this week and I'm not sure I'm doing it right. The further I get in this class the more I feel lost. :(

1. The amounts (in ounces) of juice in eight randomly selected juice bottles are:

15.4 15.7 15.2 15.8 15.8 15.4 15.0 15.6

Assuming the population of amounts in juice bottles is known to be normally distributed, create a 95% confidence interval estimate for , the mean amount of juice in all bottles.

You will be asked to identify x-bar, s, alpha, df, t, E and the confidence interval. (3 points each)


This is what I have come up with so far:
X-bar = 15.488
S = .290
alpha = .05
df = 7
T =
E =
critical value= 1.96
CI = (15.2456, 15.7304)

Is this right so far? I have a partner in my class I'm working on this with and her answers are totally different than mine.

Quote:

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Originally Posted by rclements3

this is one of my questions on my homework this week and I'm not sure I'm doing it right. The further I get in this class the more I feel lost. :(

1. The amounts (in ounces) of juice in eight randomly selected juice bottles are:

15.4 15.7 15.2 15.8 15.8 15.4 15.0 15.6

Assuming the population of amounts in juice bottles is known to be normally distributed, create a 95% confidence interval estimate for , the mean amount of juice in all bottles.

You will be asked to identify x-bar, s, alpha, df, t, E and the confidence interval. (3 points each)


This is what I have come up with so far:
X-bar = 15.488
S = .290
alpha = .05
df = 7
T =
E =
critical value= 1.96
CI = (15.2456, 15.7304)

Is this right so far? I have a partner in my class I'm working on this with and her answers are totally different than mine.

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Your critical value is wrong but somehow you got the correct confidence interval ....??
The critical value of T is 2.3646, not 1.96 (that's the critical value for Z. And you realise that Z is not used because the population sd is not known).