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? Roundup your answer to the next whole number. On= 189 On = 110 On = 425 On = 174

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