Question

Internet providers: In a survey of 780 homeowners with high-speed Internet, the average monthly cost of a high-speed Internet plan was $64.22 with standard deviation S10.75. Assume the plan costs to be approximately bell-shaped. Estimate the number of plans that cost between $42.72 and $85.72. pprosimately bell-shaped. The number of plans that cost between $42.72 and $85.72 is:_________

Answer 1

Hence the number of plans that cost between $42.72 and $ 85.72 is

95.44 %.

Explanation:

Now the given are

μ = $64.22.

σ = $10.75.

Here,

`P\left ( 42.72 < x< 85.72 \right )=P\left ( (42..72-64.22)/(10.75)< (x-\mu )/(\sigma ) < (85.72-64.22)/(10.75)\right )\\P\left ( 42.72 < x< 85.72 \right )= P\left ( -2.00< Z <2.00 \right )\\P\left ( 42.72 < x< 85.72 \right )= P\left (Z<2.00\right )-P\left ( Z<-2.00 \right )\\P\left ( 42.72 < x< 85.72 \right )= P\left (0.9772\right )-P\left (0.0228\right )\\Probability = 0.9544`

Probability = 95.44%.