In: Statistics and Probability
Solution:
We are given that: Q1 = the first quartile is 200, and Q3=the third quartile, is 240.
Part a) What is the interquartile range?
Interquartile Range = IQR = Q3 - Q1
IQR = 240 - 200
IQR = 40
Part b) A number in the data set would have to be above what number to be an outlier?
Upper Bound for an outlier = Q3 + 1.5 X IQR
Upper Bound for an outlier = 240 + 1.5 X 40
Upper Bound for an outlier = 240 + 60
Upper Bound for an outlier = 300
Thus a number in the data set would have to be above 300 to be an outlier.
Part c) A number in the data set would have to be below what number to be an outlier?
Lower Bound for an outlier = Q1 - 1.5 X IQR
Lower Bound for an outlier = 200 - 1.5 X 40
Lower Bound for an outlier = 200 - 60
Lower Bound for an outlier = 140
A number in the data set would have to be below 140 to be an outlier.
Part d) Which of the following numbers are outliers? 100 150 280 330
100 is below 140, hence it is an outlier.
150 and 280 are in between lower and upper bounds, hence these two numbers are not an outliers.
330 is above upper bound 300, hence 330 is an outlier.