Question

question 19
for the scores in the following table, what is the value of σx²?
x f
3 1
2 2
1 4
23
15
11
21
question 20
a set of scores ranges from x = 13 to x = 73. if the scores were put in a grouped frequency distribution table with an interval width, the top interval would be 73 - 82.
true
false

Explanation:

Step1: Calculate \(X^{2}f\) for each row

For \(X = 3,f = 1\), \(X^{2}f=3^{2}\times1 = 9\); for \(X = 2,f = 2\), \(X^{2}f=2^{2}\times2=8\); for \(X = 1,f = 4\), \(X^{2}f=1^{2}\times4 = 4\).

Step2: Sum up the \(X^{2}f\) values

\(\sum X^{2}=\ 9 + 8+4=21\)

for Question 20:
Grouped - frequency distribution intervals usually have a width of 10. The highest score is \(X = 73\), so the top - interval should be \(70 - 79\) (assuming a width of 10), not \(73 - 82\).

Answer:

21