# statistics

uatoooonec
The standard deviation of sample means is the same as the population standard deviation.

The distribution of sample means (x-bar values) for large random samples follows a bell-shaped curve only if the individual population values follow a normal distribution. (Hint: see the “Conditions for the Rule for Sample Means”).

“A 95% confidence interval for the mean weight loss for men is 6.4 to 11.2 pounds.” This means that 95% of all men will lose between 6.4 and 11.2 pounds.

If a 95% confidence interval calculated for the difference between two population means is –4.31 to 0.76, then we may conclude with high confidence that the two population means have different values.

The weights for a population of North American raccoons has a bell-shaped frequency curve with a mean of about 12 pounds and a standard deviation of about 2.5 pounds.
About 95% of the weights for individual raccoons in this population fall between what two values?

The weights for a population of North American raccoons has a bell-shaped frequency curve with a mean of about 12 pounds and a standard deviation of about 2.5 pounds.
About 95% of the weights for individual raccoons in this population fall between what two values?

The weights for a population of North American raccoons has a bell-shaped frequency curve with a mean of about 12 pounds and a standard deviation of about 2.5 pounds.
About 95% of the mean weights from samples of size 25 raccoons from this population fall between what two values?

The Baltimore Sun (Haney, 21 February 1995) reported on a study by Dr. Sara Harkness, in which she observed the sleep patterns of 6-month-old infants. She found that a sample of n = 49 infants in the U.S. slept an average of 13 hours per day, and that the standard deviation of this sample was 0.5 hours.
Compute a 90% confidence interval for the mean sleep time per day for 6-month-old infants in the U.S.

The Baltimore Sun (Haney, 21 February 1995) reported on a study by Dr. Sara Harkness, in which she observed the sleep patterns of 6-month-old infants. She found that a sample of n = 49 infants in the U.S. slept an average of 13 hours per day, and that the standard deviation of this sample was 0.5 hours.
Interpret the confidence interval you computed above using words that someone with no training in statistics might understand.

• 6 years ago
• 10