A bookstore sells books for $2, $3, $5, and $10. Let random variable X = "amount of
money for one book."
Look at the relative-frequency table below representing the amount of money spent on
one item and the relative frequencies with which customers purchase them
If the expected amount of money spent by a customer is $3.23 what is the standard deviation?

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pranavgera011 pranavgera011 · Answer 1 · 2022-08-03T14:15:48+02:00

The value of the standard deviation is σ = 2.20. Using probability distribution, the required standard deviation is calculated.

The formula for the standard deviation of the given probability distribution is

σ = √∑([tex]x_i^2[/tex] × [tex]P(X_i)[/tex]) - μₓ²

Where the mean μₓ = ∑[[tex]x_i[/tex] × [tex]P(X_i)[/tex]]

It is given that,

x: $2, $3, $5, $10

P(X=x): 0.55, 0.26, 0.11, 0.08

Step 1: Calculating the mean:

we have μₓ = ∑[[tex]x_i[/tex] × [tex]P(X_i)[/tex]]

⇒ μₓ = 2 × 0.55 + 3 × 0.26 + 5 × 0.11 + 10 × 0.08

∴ μₓ = 3.23

Step 2: Calculating the standard deviation:

x: 2, 3, 5, 10

x²: 4, 9, 25, 100

P(X=x): 0.55, 0.26, 0.11, 0.08

([tex]x_i^2[/tex]) × [tex]P(X_i)[/tex]: 4 × 0.55 = 2.2; 9 × 0.26 = 2.34; 25 × 0.11 = 2.75; 100 × 0.08 =8

∑[([tex]x_i^2[/tex]) × [tex]P(X_i)[/tex]]: 2.2 + 2.34 + 2.75 + 8 = 15.29

Therefore,

The standard deviation, σ = √∑([tex]x_i^2[/tex] × [tex]P(X_i)[/tex]) - μₓ²

⇒ σ = [tex]\sqrt{15.29-(3.23)^2}[/tex]

= [tex]\sqrt{15.29-10.43}[/tex]

∴ σ = 2.20

Learn more about the probability distribution here:

https://brainly.com/question/18804692

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