If a score of 50 is added to the data set,
The standard deviation increases.
The range increases.
What is mean?
"It is the average of all elements of the data set."
What is median?
"It is the middle number in a sorted list of numbers."
Formula to calculate the standard deviation:
[tex]SD=\sqrt{\frac{\sum{(x-M)^{2}} }{N} }[/tex]
where, SD is the population standard deviation
N : the size of the population
x : each value from the data
M : the mean of the data
Formula to calculate the range of the data:
range = maximum value - minimum value
For given situation,
Consider the original set of test scores: 71, 75, 80, 81, 81, 84, 89, 93
N = 8
range R = 93 - 71
⇒ R = 22
Mean M = (71 + 75 + 80 + 81 + 81 + 84 + 89 + 93)/8
⇒ M = 654/8
⇒ M = 81.75
Now, we find the median K
First we sort given data set: 71, 75, 80, 81, 81, 84, 89, 93
The middle numbers are 81 and 81
So, the median is the average of 81, 81
So, K = 81
Now, we calculate the standard deviation.
[tex]SD=\sqrt{\frac{[(71-81.75)^{2}+(75-81.75)^{2}+...+(89-81.75)^{2}+(93-81.75)^{2}] }{8} }[/tex]
⇒ SD = 6.61
Consider, the set of test scores with 50 added to the data set.
N = 9
range R = 93 - 50
⇒ R = 43
Mean M = (71 + 75 + 80 + 81 + 50 + 81 + 84 + 89 + 93)/9
⇒ M = 704/9
⇒ M = 78.22
Now, we find the median K
First we sort given data set: 50, 71, 75, 80, 81, 81, 84, 89, 93
The middle number is 81.
So, the median is K = 81
Now, we calculate the standard deviation.
[tex]SD=\sqrt{\frac{[(71-81.75)^{2}+(75-81.75)^{2}+...+(50-81.75)^{2}+(93-81.75)^{2}] }{9} }[/tex]
⇒ SD = 11.76
So, we can observe that if a score of 50 is added to the data set, the correct statements are:
The standard deviation increases.
The range increases.
Learn more about mean, standard deviation, median, range here:
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