Normal Distribution, Confidence Intervals
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The lengths of pregnancies are normally distributed with a mean of 268 days and a standard deviation of 15 days. A letter was written to "Dear Abby" in which a wife claimed to have given birth 308 days after a brief visit from her husband who was serving in the Navy.
1. Find the probability of a pregnancy lasting 308 days or longer.
2. What does this result suggest?
We stipulate that a baby is premature if the length of the pregnancy is in the lowest 4%.
3. Would a baby who is born at 215 days be considered premature?
4. Find the length of pregnancy that separates premature babies from those who are not premature.
Student t Distribution - Confidence Intervals
A simple random sample of the body temperatures of 106 healthy humans were taken for which
x=98.20o F and s=0.62oF .
1. What two requirements must be satisfied to use a Student t distribution.
2. Determine the number of degrees of freedom for this sample size.
3. Construct a 99% confidence interval to estimate the mean body temperature of all healthy humans.
4. What does the confidence interval suggest about the use of 98.6o as the mean body
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