Question

A random sample of math majors taking an introductory statistics course were surveyed after completing the final exam. They were asked, "How many times did you review your final exam before handing it in to the professor? The results we displayed in a probability density function for the random variableX, the number of times students reviewed their exam before handing it in. Find the standard deviation of X. X PIX = x 1 1/5 2 2/5 5 2/5 0 2.79 11.8 3.0 1.67

Answer 1

Answer:

Calculation table:

X	p(x)	x*p(x)	x^2*p(x)
1	0.2	0.2	0.2
2	0.4	0.8	1.6
5	0.4	2	10
Total		3	11.8

$E(x)=\sum xipi$

From above table,

$E(x)=3$

$E(x^2)=\sum xi^2pi$

$E(x^2)=11.8$

$s.d(x)=\sqrt{E(x^2)-(E(x))^2}$

$s.d(x)=\sqrt{11.8-(3)^2}$

$s.d(x)=1.67$