Mel drove 432 miles during his trip. He drove an average of 72 miles per hour. How long was his trip?
2 answers:
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Answer: C) 133
Step-by-step explanation:
The formula to find the sample size is given by :-
, where z* = Critical z-value
= Population standard deviation for prior study.
E= Margin of error.
As per given , we have
E= 5
The critical z-value for 90% confidence level is 1.645.
Substitute al;l the value sin the above formula , we get
Hence, the minimum sample size needed is 133.
Thus , the correct answer is : C) 133