STT 231 EXAM 1 QUESTIONS &
ANSWERS(RATED A+)
You asked ten of your classmates about their weight. On the basis of this information,
you stated that the average weight of all students in your university or college is 142.6
pounds. This is an example of: - ANSWERstatistic
A company has developed a new battery, but the average lifetime is unknown. In order
to estimate this average, a sample of 100 batteries is tested and the average lifetime of
this sample is found to be 250 hours. Identify population, sample, variable, parameter,
and statistic. - ANSWER-Population: all new batteries
-Sample: 100 tested batteries
-Variable: battery lifetime
-Parameter: average of all tested batteries
-Statistic: average of 250 hours
What are the mean and standard deviation of z-scores? Will z-scores change the shape
of a histogram? - ANSWER-Mean will be 0 and standard deviation will be +1. Will not
change shape of histogram.
Suppose you were asked about the proportion of data within a certain interval. How
would you determine it? - ANSWER-First find the mean and the standard deviation.
-Then we can calculate the z-scores for the interval by subtracting each value of the
interval by the mean and then dividing by the standard deviation.
-According to Chebyshev's rule, we can then say then say z-score="k" and find the
proportion of data based on (1-1/k^2)
What information can we gather from a scatter plot? - ANSWER-Its direction (positive or
negative)
-Its form (linear or non-linear)
-Its strength (r-value)
-unusual features (outliers or clusters)
What is the correlation coefficient? Describe its features. - ANSWER-Describes linear
association between two quantitative variables.
-Its units do not matter and it will not change if data is scaled.
-It has direction and magnitude: direction is determined by sign and strength is
determined by magnitude.
-OUTLIER sensitive
What are the regression coefficients of the linear regression model? - ANSWER-a=b1
while b=b0 (y=ax+b)
-"regression line of Y on X"
ANSWERS(RATED A+)
You asked ten of your classmates about their weight. On the basis of this information,
you stated that the average weight of all students in your university or college is 142.6
pounds. This is an example of: - ANSWERstatistic
A company has developed a new battery, but the average lifetime is unknown. In order
to estimate this average, a sample of 100 batteries is tested and the average lifetime of
this sample is found to be 250 hours. Identify population, sample, variable, parameter,
and statistic. - ANSWER-Population: all new batteries
-Sample: 100 tested batteries
-Variable: battery lifetime
-Parameter: average of all tested batteries
-Statistic: average of 250 hours
What are the mean and standard deviation of z-scores? Will z-scores change the shape
of a histogram? - ANSWER-Mean will be 0 and standard deviation will be +1. Will not
change shape of histogram.
Suppose you were asked about the proportion of data within a certain interval. How
would you determine it? - ANSWER-First find the mean and the standard deviation.
-Then we can calculate the z-scores for the interval by subtracting each value of the
interval by the mean and then dividing by the standard deviation.
-According to Chebyshev's rule, we can then say then say z-score="k" and find the
proportion of data based on (1-1/k^2)
What information can we gather from a scatter plot? - ANSWER-Its direction (positive or
negative)
-Its form (linear or non-linear)
-Its strength (r-value)
-unusual features (outliers or clusters)
What is the correlation coefficient? Describe its features. - ANSWER-Describes linear
association between two quantitative variables.
-Its units do not matter and it will not change if data is scaled.
-It has direction and magnitude: direction is determined by sign and strength is
determined by magnitude.
-OUTLIER sensitive
What are the regression coefficients of the linear regression model? - ANSWER-a=b1
while b=b0 (y=ax+b)
-"regression line of Y on X"
