In a survey, 28 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $41 and standard deviation of $5. Construct a confidence interval at a 90% confidence interval .
I used E = t(alpha/2) * s / sqrt(n)
i got a t critical value of 1.703, i got it wrong

Question

In a survey, 28 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $41 and standard deviation of $5. Construct a confidence interval at a 90% confidence interval .
I used  E = t(alpha/2) * s / sqrt(n)
i got a t critical value of 1.703, i got it wrong

anonymous · Answer

Alright, so I can help you here, but first do you know how to find the mean of this question?

perl · Answer

hello

perl · Answer

thank you so much

perl · Answer

we just want to a confidence interval around the population mean, we dont need to know the actual population mean

anonymous · Answer

Alright, give me a few minutes to figure this out.

perl · Answer

i got all the calculations , let me give you a website

anonymous · Answer

ok

perl · Answer

here are some rules http://www.ghamsary.elac.org/lecture/Statistics_chap06.pdf

perl · Answer

and we can find the t critical value using a TI 83

anonymous · Answer

Alright do you know how to use the plot function on your calculator? for finding the critical value?

perl · Answer

yes, 
invT( 1-.1/2, 27 ) , because there are 27 degrees of freedom

anonymous · Answer

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