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1. Hey!

I have a statistic question I want some help with (like which formulas to use etc.). Here it comes:

1. A medical researcher wants to investigate the amount of time it takes for patients' headache pain to be relieved after taking a new prescription painkiller. She plans to use statistical methods to estimate the mean of the population of relief times. She believes that the population is normally distributed with a standard deviation of 20 minutes. How large a sample should she take to estimate the mean time to within 1 minutes with 90% confidence?
2. (Original post by SikoSiko)
Hey!

I have a statistic question I want some help with (like which formulas to use etc.). Here it comes:

1. A medical researcher wants to investigate the amount of time it takes for patients' headache pain to be relieved after taking a new prescription painkiller. She plans to use statistical methods to estimate the mean of the population of relief times. She believes that the population is normally distributed with a standard deviation of 20 minutes. How large a sample should she take to estimate the mean time to within 1 minutes with 90% confidence?
within 1 minute above or below the true mean

σ / √n * φ-1(0.95) = 1

sub in and rearrange

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