Psych 320/L – Mark P. Otten
Homework 1
Jairo Peralta PSY 320
1. A question on a student survey asks: In a typical week, how many times do
you eat at a fast food restaurant? The following data was then collected:
No. of times per week No. of students
5 or more 2
4 2
3 3
2 6
1 0
0 3
A. Find the mode (number of times per week) for this data.
Mode = 2
B. Find the median (number of times per week) for this data.
0,0,0,2,2,2,2,2,2,3,3,3,4,4,5,5
Median = 2
C. Explain why you cannot compute the mean number of times per week using
the data in the table.
You cannot take the mean as the table shows categorical data and the mode is
more useful. It wouldn't make sense to take the mean.
2. A sample of n = 7 scores has a mean of 5. After one score is added to the
sample, the new mean is found to be 7. What is the value of the new score?
(Hint: compare the values for ∑X before and after the score is added.)
Mean (5) = ∑X/n Mean (7) = ∑X/n
5 x (n) = ∑X/n x n 7 x (n) = ∑X/n x n
5 x 7 = ∑X 7 x 7 = ∑X
35 = ∑X old value 49 = ∑X new value
3. What does it mean for a sample to have a standard deviation of zero?
Describe the scores in such a sample.
That would mean all the data has the same value as the mean. For example:
90,90,90,90,90. Mean = 90. (X – mean) would equal zero for each number. (X –
mean) ^2 would also equal zero for each number. Sum of Squares, Variance and
Standard Deviation would all equal zero.
4. Explain what it means to say that the sample variance provides an unbiased
estimate of the population variance.
This study source was downloaded by 100000832445974 from CourseHero.com on 09-07-2023 04:21:37 GMT -05:00
https://www.coursehero.com/file/69698830/Homework-1-Statisticsdocx/
Homework 1
Jairo Peralta PSY 320
1. A question on a student survey asks: In a typical week, how many times do
you eat at a fast food restaurant? The following data was then collected:
No. of times per week No. of students
5 or more 2
4 2
3 3
2 6
1 0
0 3
A. Find the mode (number of times per week) for this data.
Mode = 2
B. Find the median (number of times per week) for this data.
0,0,0,2,2,2,2,2,2,3,3,3,4,4,5,5
Median = 2
C. Explain why you cannot compute the mean number of times per week using
the data in the table.
You cannot take the mean as the table shows categorical data and the mode is
more useful. It wouldn't make sense to take the mean.
2. A sample of n = 7 scores has a mean of 5. After one score is added to the
sample, the new mean is found to be 7. What is the value of the new score?
(Hint: compare the values for ∑X before and after the score is added.)
Mean (5) = ∑X/n Mean (7) = ∑X/n
5 x (n) = ∑X/n x n 7 x (n) = ∑X/n x n
5 x 7 = ∑X 7 x 7 = ∑X
35 = ∑X old value 49 = ∑X new value
3. What does it mean for a sample to have a standard deviation of zero?
Describe the scores in such a sample.
That would mean all the data has the same value as the mean. For example:
90,90,90,90,90. Mean = 90. (X – mean) would equal zero for each number. (X –
mean) ^2 would also equal zero for each number. Sum of Squares, Variance and
Standard Deviation would all equal zero.
4. Explain what it means to say that the sample variance provides an unbiased
estimate of the population variance.
This study source was downloaded by 100000832445974 from CourseHero.com on 09-07-2023 04:21:37 GMT -05:00
https://www.coursehero.com/file/69698830/Homework-1-Statisticsdocx/
