A random 2

A random sample of 40 families has an average water consumption of 29 cubic meters per month, with a sample standard deviation of 8 cubic meters. Give the 90% confidence interval for the mean usage of water per month.

Correct answer:

a =  26.9192 m3
b =  31.0808 m3

Step-by-step explanation:

n=40 m=29 m3 σ=8 m3  p=90%=10090=109=0.9  s=nσ=4081.2649   (100  90) % / 2 = 5 % z0=1.645  e=z0 s=1.645 1.26492.0808 m3  a=me=292.0808=26.9192 m3
b=m+e=29+2.0808=31.0808 m3



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