A sixth grade teacher can grade 40 math assignments in 20 minutes. How many assignments can she grade in 1 minute?
2 answers:
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Answer:
a. n=4148
b. n=3909
c. The sample size is smaller if a known proportion from prior study is used. The difference in sample sizes is 239
Step-by-step explanation:
a. For sample where no preliminary estimate is given, the minimum sample size is calculated using the formula:
Where:
Margin of error
is the assumed proportion
#Let p=0.5, substitute in the formula to solve for n:
Hence, the minimum sample size is 4148
b. If given a preliminary estimate p=0.38, we use the same formula but substitute p with the given value:
Hence, the minimum sample size is 3909
c. Comparing the sample sizes from a and b:
Hence, the actual sample size is smaller for a known proportion from prior a prior study.