UGS 303 – Spring, 2011
Some practice.
First, some equations:
Mode = most frequently occurring score(s)
Location of first quartile,
Location of second quartile, or median,
Location of third quartile,
Q1: X.25 = (N+1) (.25)
Q2: X.50 = (N+1) (.50)
Q3: X.75 = (N+1) (.75)
Mean = µ = ΣX/N
Range = value of highest score minus value of lowest score
SIQR = (Q3 – Q1)/2
σ = SQRT(Σ(X - µ)2/N)
First scenario
I asked 12 people how many cars they had owned in their lives. Here are the answers I
got:
10
1
4
8
8
2
3
6
3
5
9
7
1. Draw a histogram.
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2. Create a frequency distribution with the following columns:
a. X
b. Freq(X)
c. Cumu Freq(X)
3.
4.
5.
6.
7.
8.
9.
What’s the mode of this distribution?
Median?
Mean?
Range?
SIQR?
Standard Deviation?
What is the value of “N”?
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10. For a distribution of scores, the median is 140 and the mean is 160. What might I
conclude about the distribution? __________________________
11. Here’s a distribution of scores:
What’s the mode of this distribution?
What’s the mean of this distribution?
Median?
Range?
SIQR?
Standard Deviation?
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12. I have a distribution of 1000 scores. It is distributed normally. The range is from
10 to 60. I CHANGE the lowest score from 10 to 1.
a) What happens to the mode?
____________
b) What happens to the median?
____________
c) What happens to the mean?
____________
d) What happens to the range?
____________
e) What happens to the SIQR?
____________
f) What happens to the standard deviation?
____________
g) Is it still normally distributed?
____________
NOTE: I WILL ask you to bring a calculator to the midterm. I may ask you to calculate
means, or medians, or ranges. I will not ask you to calculate a standard deviation or an
SIQR.
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