Assume standard deviation of all invoices is $200. Sample 100 invoices. What is the standard deviation of xbar

Step-by-step explanation:

Standard deviation of the mean is expressed as:

SM = s/√n

s is the standard deviation of all invoices

n is the sample size of the invoiced

Given

s = $200

n = 100

Required

Standard deviation of the mean

Substitute the given parameters into the given equation

SM = 200/√100

SM = 200/10

SM = 20

Hence the standard deviation of xbar is 20

hello,

b) 62.47% of the students are between 14 and 18 years old.

step-by-step explanation:

mean = 15 and standard deviation = 2

student between 14 to 18

formula used z-score

for age 14 , z score

using z-table , p(z> -0.5)=0.3085

for age 18 , z score

using z-table , p(z< 1.5)=0.9332

p(-0.5< z< 1.5)=0.9332-0.3085 = 0.6247

thus, 62.47% of the students are between 14 and 18 years old.

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