Question

Past experience indicates that the standard deviation of the time it takes for a dentist to perform dental scaling for patients is 4 minutes. A researcher wishes to estimate the mean time to perform dental scaling with 95 percent confidence and a margin of error of ± 0.75 minutes. Given this, what must the sample size be? Round up your answer to the next whole number.

Answer 1

n = 110

Explanation:

Margin of Error :

Zcritical * s/ sqrt(n)

s = standard deviation = 4

Margin of Error = ±0.75

Zcritical at 95% level of confidence = 1.96

Margin of Error = Zcritical * s/ sqrt(n)

0.75 = 1.96 * 4 / sqrt(n)

0.75 = 7.84 / sqrt(n)

Take the square of both sides

0.5625 = 61.4656 / n

0.5625 * n = 61.4656

0.5625 = 61.4656

n = 61.4656 / 0.5625

n = 109.27217

About 110 samples