BISC 305 Exam 2 practice problems
QUESTIONS & ANSWERS
Let the population random variable Y be normal with mean 2 and standard deviation 6.
Randomly choose 9 samples from the population. Let bar(Y) be the sample mean. What is the
mean of the sample mean, E(bar(Y))? - Answers:y=2
Same as problem 1. What is the standard error of the sample mean? - Answers:SE=2
Same as problem 1. What is the probability that the sample mean is less than 3? - Answers:0.69
An researcher wants to study the mean cholestrol level in a population. He sampled 9 individuals
and measured their cholesterol levels. The sample mean is 140 and the sample standard deviation
is 30. What is the lower limit of the 95% confidence interval (two sided) for the population mean
cholesterol level? - Answers:117
Same as Problem 4. Now the investigator only wants the one-sided lower 95% CI. What is the
lower limit? - Answers:121
In a study, a researcher finds the 95% confidence interval of the population mean is (2, 5). He
has 95% confidence that the interval (2, 5) contains the true population mean.
TRUE OR FALSE - Answers:TRUE
Same as problem 6. The probability that the population mean is in the interval (2, 5) is 0.95.
TRUE OR FALSE - Answers:FALSE
A scientist recorded the tail lengths (in cm) of twovarieties of woodland salamanders: redbacked
and leadbacked. The data is as follows.
Redbacked leadbacked
mean 3.0 4.0
s11
QUESTIONS & ANSWERS
Let the population random variable Y be normal with mean 2 and standard deviation 6.
Randomly choose 9 samples from the population. Let bar(Y) be the sample mean. What is the
mean of the sample mean, E(bar(Y))? - Answers:y=2
Same as problem 1. What is the standard error of the sample mean? - Answers:SE=2
Same as problem 1. What is the probability that the sample mean is less than 3? - Answers:0.69
An researcher wants to study the mean cholestrol level in a population. He sampled 9 individuals
and measured their cholesterol levels. The sample mean is 140 and the sample standard deviation
is 30. What is the lower limit of the 95% confidence interval (two sided) for the population mean
cholesterol level? - Answers:117
Same as Problem 4. Now the investigator only wants the one-sided lower 95% CI. What is the
lower limit? - Answers:121
In a study, a researcher finds the 95% confidence interval of the population mean is (2, 5). He
has 95% confidence that the interval (2, 5) contains the true population mean.
TRUE OR FALSE - Answers:TRUE
Same as problem 6. The probability that the population mean is in the interval (2, 5) is 0.95.
TRUE OR FALSE - Answers:FALSE
A scientist recorded the tail lengths (in cm) of twovarieties of woodland salamanders: redbacked
and leadbacked. The data is as follows.
Redbacked leadbacked
mean 3.0 4.0
s11
