STT 215 FINAL EXAM QUESTIONS WITH VERIFIED
ANSWERS LATEST UPDATED
For the following pairs of variables, which more naturally is the response
variable and which is the explanatory variable?
a. sales and advertising - ANSWER sales is the response variable because it is
the outcome variable on which comparisons are made and advertising is the
explanatory variable.
for the following pairs of variables, which more naturally is the response
variable and which is the explanatory variable?
b. grade received and effort - ANSWER grade received is the response
variable because it is the outcome variable on which comparisons are made and
effort made is the explanatory variable.
for the following pairs of variables which more naturally is the response
variable and which is the explanatory variable?
c. number of children and mother's age - ANSWER number of children is the
response variable because it is the outcome variable on which comparisons are
made and mother's age is the explanatory variable.
sixty mice that are susceptible to cancer are randomly divided into two groups.
one group is treated daily with radiation similar to that generated by cell phones.
the other group receives no radiation. after one year, both groups are tested for
cancer.
a. identify the response variable and the explanatory variable. - ANSWER the
response variable is the presence of cancer and the explanatory variable is
whether or not cell phone radiation was received.
sixty mice that are susceptible to cancer are randomly divided into two groups.
one group is treated daily with radiation similar to that generated by cell phones.
the other group receives no radiation. after one year, both groups are tested for
cancer.
b. was this an observational study or an experiment? explain why. - ANSWER
the study is an experiment because the researchers assign subjects to certain
experimental conditions and observe the outcomes on the response variable.
,an opinion survey was conducted by a graduate student. the student polled 1626
teachers, asking their opinions on the funding of education in their state. he
received back questionnaires from 186 teachers, 66 of whom indicated that their
school was underfunded.
a. what was the population for this survey? - ANSWER teachers
an opinion survey was conducted by a graduate student. the student polled 1626
teachers, asking their opinions on the funding of education in their state. he
received back questionnaires from 186 teachers, 66 of whom indicated that their
school was underfunded.
b. what was the intended sample size?
what was the sample size actually observed?
what was the percentage of nonresponse? - ANSWER 1626
186
88.6% (1626-186=1440) (1440/1626=0.8856)
an opinion survey was conducted by a graduate student. the student polled 1626
teachers, asking their opinions on the funding of education in their state. he
received back questionnaires from 186 teachers, 66 of whom indicated that their
school was underfunded.
c. what are two potential sources of bias with this survey? - ANSWER
nonresponse bias and sampling bias
is there a relationship between the weight and price of a mountain bike? the
following data set gives the weights and prices for ten mountain bikes. let the
explanatory variable x be the weight in pounds and the response variable y be
the bike's price.
weight: 33 29 28 34 29 28 34 31 36 27
price: 360 1080 690 920 570 470 190 980 150 590
a. construct a scatterplot. interpret. - ANSWER (put numbers into excel and hit
scatterplot)
the scatter plot shows a moderate negative association between the two
variables.
is there a relationship between the weight and price of a mountain bike? the
following data set gives the weights and prices for ten mountain bikes. let the
,explanatory variable x be the weight in pounds and the response variable y be
the bike's price.
weight: 33 29 28 34 29 28 34 31 36 27
price: 360 1080 690 920 570 470 190 980 150 590
b. find the regression equation. interpret the slope in context. does the y-
intercept have contextual meaning? - ANSWER the regression equation is
y=1899.96+(-42.07)x
the slope means that as the weight of a mountain bike increases by one pound,
the cost tends to decrease by 42.07 dollars.
the y-intercept is the cost of a mountain bike that weights 0 pounds. since there
are no observations with such x-values, the y-intercept does not have contextual
meaning.
https://www.socscistatistics.com/tests/regression/default.aspx
is there a relationship between the weight and price of a mountain bike? the
following data set gives the weights and prices for ten mountain bikes. let the
explanatory variable x be the weight in pounds and the response variable y be
the bike's price.
weight: 33 29 28 34 29 28 34 31 36 27
price: 360 1080 690 920 570 470 190 980 150 590
c. you decide to purchase a mountain bike that weighs 35 pounds. what is the
predicted price for the bike? - ANSWER the predicted price of a mountain
bike that weighs 35 pounds is $427.51
for 39 nations, a correlation of 0.883 was found between y=internet use (%) and
x=gross domestic product (GPD, in thousands of dollars per capita). the
regression equation is y=-3.75+1.17x.
a. based on the correlation value, the slope had to be positive. why? -
ANSWER although slope and correlation usually have different values, they
always have the same sign.
for 39 nations, a correlation of 0.883 was found between y=internet use (%) and
x=gross domestic product (GPD, in thousands of dollars per capita). the
regression equation is y=-3.75+1.17x.
b. one nation had a GPD of 27.2 thousand dollars and internet use of 30.8%.
find its predicted internet use based on the regression equation. - ANSWER
28.1
(y=-3.75+1.17(27.2))
, for 39 nations, a correlation of 0.883 was found between y=internet use (%) and
x=gross domestic product (GPD, in thousands of dollars per capita). the
regression equation is y=-3.75+1.17x.
c. find the residual for this nation. - ANSWER 2.7
(30.8-28.1)
the job placement center at your school surveys 90% of all graduating seniors at
the school. their report about the survey provides numerical summaries such as
the average starting salary and the percentage of students earning more than
$35,000 a year.
a. are the statistical analyses descriptive or inferential statistics? - ANSWER
descriptive, because they summarize the data collected.
the job placement center at your school surveys 90% of all graduating seniors at
the school. their report about the survey provides numerical summaries such as
the average starting salary and the percentage of students earning more than
$35,000 a year.
b. are these numerical summaries better characterized as statistics or as
parameters? - ANSWER statistics, because the analyses summarize data on a
sample.
for the following variable, indicate whether one would expect its histogram to
be symmetric, skewed to the right, or skewed to the left. explain why.
the weekly church contributions for all members of a congregation, in which the
three wealthiest members contribute generously each week. - ANSWER one
would expect the histogram to be skewed to the right because the majority of
weekly contributions would be lower values, with some higher values.
consider an experiment being designed to study the effectiveness of an
experimental pain reduction medication. the plan includes recruiting 100
individuals suffering from moderate to severe pain to participate. one half of the
group will be assigned to take the experimental drug and the other half will be
assigned a placebo. the study will be blind, so the individuals will not know
which treatment they are receiving. at the end of the study, they will be asked to
record how much pain relief they experienced. why is it important to use a
placebo in this study? - ANSWER without a placebo, or a control comparison
group, there is no way to differentiate between the placebo effect and the actual
ANSWERS LATEST UPDATED
For the following pairs of variables, which more naturally is the response
variable and which is the explanatory variable?
a. sales and advertising - ANSWER sales is the response variable because it is
the outcome variable on which comparisons are made and advertising is the
explanatory variable.
for the following pairs of variables, which more naturally is the response
variable and which is the explanatory variable?
b. grade received and effort - ANSWER grade received is the response
variable because it is the outcome variable on which comparisons are made and
effort made is the explanatory variable.
for the following pairs of variables which more naturally is the response
variable and which is the explanatory variable?
c. number of children and mother's age - ANSWER number of children is the
response variable because it is the outcome variable on which comparisons are
made and mother's age is the explanatory variable.
sixty mice that are susceptible to cancer are randomly divided into two groups.
one group is treated daily with radiation similar to that generated by cell phones.
the other group receives no radiation. after one year, both groups are tested for
cancer.
a. identify the response variable and the explanatory variable. - ANSWER the
response variable is the presence of cancer and the explanatory variable is
whether or not cell phone radiation was received.
sixty mice that are susceptible to cancer are randomly divided into two groups.
one group is treated daily with radiation similar to that generated by cell phones.
the other group receives no radiation. after one year, both groups are tested for
cancer.
b. was this an observational study or an experiment? explain why. - ANSWER
the study is an experiment because the researchers assign subjects to certain
experimental conditions and observe the outcomes on the response variable.
,an opinion survey was conducted by a graduate student. the student polled 1626
teachers, asking their opinions on the funding of education in their state. he
received back questionnaires from 186 teachers, 66 of whom indicated that their
school was underfunded.
a. what was the population for this survey? - ANSWER teachers
an opinion survey was conducted by a graduate student. the student polled 1626
teachers, asking their opinions on the funding of education in their state. he
received back questionnaires from 186 teachers, 66 of whom indicated that their
school was underfunded.
b. what was the intended sample size?
what was the sample size actually observed?
what was the percentage of nonresponse? - ANSWER 1626
186
88.6% (1626-186=1440) (1440/1626=0.8856)
an opinion survey was conducted by a graduate student. the student polled 1626
teachers, asking their opinions on the funding of education in their state. he
received back questionnaires from 186 teachers, 66 of whom indicated that their
school was underfunded.
c. what are two potential sources of bias with this survey? - ANSWER
nonresponse bias and sampling bias
is there a relationship between the weight and price of a mountain bike? the
following data set gives the weights and prices for ten mountain bikes. let the
explanatory variable x be the weight in pounds and the response variable y be
the bike's price.
weight: 33 29 28 34 29 28 34 31 36 27
price: 360 1080 690 920 570 470 190 980 150 590
a. construct a scatterplot. interpret. - ANSWER (put numbers into excel and hit
scatterplot)
the scatter plot shows a moderate negative association between the two
variables.
is there a relationship between the weight and price of a mountain bike? the
following data set gives the weights and prices for ten mountain bikes. let the
,explanatory variable x be the weight in pounds and the response variable y be
the bike's price.
weight: 33 29 28 34 29 28 34 31 36 27
price: 360 1080 690 920 570 470 190 980 150 590
b. find the regression equation. interpret the slope in context. does the y-
intercept have contextual meaning? - ANSWER the regression equation is
y=1899.96+(-42.07)x
the slope means that as the weight of a mountain bike increases by one pound,
the cost tends to decrease by 42.07 dollars.
the y-intercept is the cost of a mountain bike that weights 0 pounds. since there
are no observations with such x-values, the y-intercept does not have contextual
meaning.
https://www.socscistatistics.com/tests/regression/default.aspx
is there a relationship between the weight and price of a mountain bike? the
following data set gives the weights and prices for ten mountain bikes. let the
explanatory variable x be the weight in pounds and the response variable y be
the bike's price.
weight: 33 29 28 34 29 28 34 31 36 27
price: 360 1080 690 920 570 470 190 980 150 590
c. you decide to purchase a mountain bike that weighs 35 pounds. what is the
predicted price for the bike? - ANSWER the predicted price of a mountain
bike that weighs 35 pounds is $427.51
for 39 nations, a correlation of 0.883 was found between y=internet use (%) and
x=gross domestic product (GPD, in thousands of dollars per capita). the
regression equation is y=-3.75+1.17x.
a. based on the correlation value, the slope had to be positive. why? -
ANSWER although slope and correlation usually have different values, they
always have the same sign.
for 39 nations, a correlation of 0.883 was found between y=internet use (%) and
x=gross domestic product (GPD, in thousands of dollars per capita). the
regression equation is y=-3.75+1.17x.
b. one nation had a GPD of 27.2 thousand dollars and internet use of 30.8%.
find its predicted internet use based on the regression equation. - ANSWER
28.1
(y=-3.75+1.17(27.2))
, for 39 nations, a correlation of 0.883 was found between y=internet use (%) and
x=gross domestic product (GPD, in thousands of dollars per capita). the
regression equation is y=-3.75+1.17x.
c. find the residual for this nation. - ANSWER 2.7
(30.8-28.1)
the job placement center at your school surveys 90% of all graduating seniors at
the school. their report about the survey provides numerical summaries such as
the average starting salary and the percentage of students earning more than
$35,000 a year.
a. are the statistical analyses descriptive or inferential statistics? - ANSWER
descriptive, because they summarize the data collected.
the job placement center at your school surveys 90% of all graduating seniors at
the school. their report about the survey provides numerical summaries such as
the average starting salary and the percentage of students earning more than
$35,000 a year.
b. are these numerical summaries better characterized as statistics or as
parameters? - ANSWER statistics, because the analyses summarize data on a
sample.
for the following variable, indicate whether one would expect its histogram to
be symmetric, skewed to the right, or skewed to the left. explain why.
the weekly church contributions for all members of a congregation, in which the
three wealthiest members contribute generously each week. - ANSWER one
would expect the histogram to be skewed to the right because the majority of
weekly contributions would be lower values, with some higher values.
consider an experiment being designed to study the effectiveness of an
experimental pain reduction medication. the plan includes recruiting 100
individuals suffering from moderate to severe pain to participate. one half of the
group will be assigned to take the experimental drug and the other half will be
assigned a placebo. the study will be blind, so the individuals will not know
which treatment they are receiving. at the end of the study, they will be asked to
record how much pain relief they experienced. why is it important to use a
placebo in this study? - ANSWER without a placebo, or a control comparison
group, there is no way to differentiate between the placebo effect and the actual
