A psychologist is trying to determine how many hours the average person sleeps each night. He takes a random sample of 25 individuals and asks each person how many hours he or she slept the previous night. The sum of the observations and the sum of the squared observations are: Estimate with 99% confidence the mean number of hours of sleep.
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Sleep

A natural, reversible state of reduced responsiveness to external stimuli and diminished activity of the body, essential for physical and mental restoration.

Confidence

The degree of certainty or trust one can place in a particular result or conclusion, often expressed as a percentage in statistical analyses.

Observations

Elements of a sample or population that have been collected and can be analyzed statistically.