STAT 121 Exam 2025 Practice Questions
Verified Answers
The probability of an event can be defined as
the fraction of time the event will occur if the random phenomenon is
repeated many times.
The Central Limit Theorem tells us that under certain conditions
the shape of the sampling distribution of x ̄will be approximately Normal.
On a control chart, under what circumstance is the process out of control?
-A run of 9 consecutive sample means above the centerline or below the centerline
-A sample mean below the lower limit
-A sample mean above the upper limit
Which one of the following is not a statistic?
μ
Control charts are designed to sound an alarm when
the amount of observed variation exceeds the amount that could be attributable to
natural variation.
Twenty-five right-handed men were tested to compare their right hand strength with their left
hand strength using a bathroom scale. For each male, a coin was tossed. If it landed heads, the
man first squeezed the scales with his right hand and then with his left hand. If the coin landed
tails, the man squeezed the scales with his left hand first and then with his right. The weight
registered on the scale is recorded for both hands. What type of study is this?
Matched pairs experiment
The Central Limit Theorem says that
, the sampling distribution of x ̄is approximately Normal when the samples are
large and random.
The Central Limit Theorem on x̄requires
a large random sample.
The standard deviation of the sampling distribution of x ̄is _____________ the standard
deviation of the population from which samples of size n >1 are taken to create the
sampling distribution.
less than
The mean score of the fourth exam in a statistics class with 1800 students at a large
university was 79 with a standard deviation of 14. Suppose twenty-five students are to be
randomly selected and their sample mean computed. What will be the mean and standard
deviation of the sampling distribution of x̄?
79.0, 2.8
When you play solitaire, you either win or lose. Therefore, the probability of winning,
according to its definition, is
approximated by playing lots of times and dividing the number of times you win by the
number of times you play.
Lifetimes of a particular flashlight battery have a non-Normal distribution with mean, μ, of
35.6 hours and standard deviation σ = 5.4 hours. A quality inspector is planning to take a
random sample of 43 of these batteries and compute the sample mean. Can he compute the
probability that the sample mean will exceed 35.7 hours using the standard Normal table?
Why or why not?
Yes, because the sample will be large and random so the Central Limit Theorem applies.
Referring to the above question and assuming that computing the probability is okay, what
is the probability that the sample mean exceeds 35.7?
Verified Answers
The probability of an event can be defined as
the fraction of time the event will occur if the random phenomenon is
repeated many times.
The Central Limit Theorem tells us that under certain conditions
the shape of the sampling distribution of x ̄will be approximately Normal.
On a control chart, under what circumstance is the process out of control?
-A run of 9 consecutive sample means above the centerline or below the centerline
-A sample mean below the lower limit
-A sample mean above the upper limit
Which one of the following is not a statistic?
μ
Control charts are designed to sound an alarm when
the amount of observed variation exceeds the amount that could be attributable to
natural variation.
Twenty-five right-handed men were tested to compare their right hand strength with their left
hand strength using a bathroom scale. For each male, a coin was tossed. If it landed heads, the
man first squeezed the scales with his right hand and then with his left hand. If the coin landed
tails, the man squeezed the scales with his left hand first and then with his right. The weight
registered on the scale is recorded for both hands. What type of study is this?
Matched pairs experiment
The Central Limit Theorem says that
, the sampling distribution of x ̄is approximately Normal when the samples are
large and random.
The Central Limit Theorem on x̄requires
a large random sample.
The standard deviation of the sampling distribution of x ̄is _____________ the standard
deviation of the population from which samples of size n >1 are taken to create the
sampling distribution.
less than
The mean score of the fourth exam in a statistics class with 1800 students at a large
university was 79 with a standard deviation of 14. Suppose twenty-five students are to be
randomly selected and their sample mean computed. What will be the mean and standard
deviation of the sampling distribution of x̄?
79.0, 2.8
When you play solitaire, you either win or lose. Therefore, the probability of winning,
according to its definition, is
approximated by playing lots of times and dividing the number of times you win by the
number of times you play.
Lifetimes of a particular flashlight battery have a non-Normal distribution with mean, μ, of
35.6 hours and standard deviation σ = 5.4 hours. A quality inspector is planning to take a
random sample of 43 of these batteries and compute the sample mean. Can he compute the
probability that the sample mean will exceed 35.7 hours using the standard Normal table?
Why or why not?
Yes, because the sample will be large and random so the Central Limit Theorem applies.
Referring to the above question and assuming that computing the probability is okay, what
is the probability that the sample mean exceeds 35.7?
