A particular brand of coffee contains an average of 112 mg of caffeine per cup with a standard deviation of 20 mg. A barista wants to investigate the same to estimate the true population mean caffeine content correct to within 5 mg adopting 95% confidence. How many cups of the same brand of coffee does he need for a sample?
The critical value for is
The corresponding confidence interval is computed as shown below:
Substitute
He needs 61 cups of the same brand of coffee for a sample.
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