Question

Determine the following: A. P(X > 654) for N(650, 10) B. P(Z < 0.72) Solution: A. 1 – pnorm(654,650,10) = 0.3445783 B. qnorm(0.72) = 0.5828415 What was done wrong in this solution?

Answer 1

a) We have the following distribution
`X \sim N(\mu =650, \sigma =10)`

And we want to calculate:

`P(X>654)`

And in order to calclate this in the ti 84 we can use the following code

2nd> Vars>DISTR

And then we need to use the following code:

1-normalcdf(-1000,654,650,10)

And we got:

`P(X>654)=0.3445783`

b) For this case we assume a normal standard distribution and we want to calculate:

`P(z<0.72)`

And using the following code in the Ti84 or using the normal standard table we got:

normalcdf(-1000,0.72,0,1)

`P(z<0.72)=0.76424`

So this part was the wrong solution from the solution posted,

Explanation:

Part a

We have the following distribution
`X \sim N(\mu =650, \sigma =10)`

And we want to calculate:

`P(X>654)`

And in order to calclate this in the ti 84 we can use the following code

2nd> Vars>DISTR

And then we need to use the following code:

1-normalcdf(-1000,654,650,10)

And we got:

`P(X>654)=0.3445783`

Part b

For this case we assume a normal standard distribution and we want to calculate:

`P(z<0.72)`

And using the following code in the Ti84 or using the normal standard table we got:

normalcdf(-1000,0.72,0,1)

`P(z<0.72)=0.76424`

So this part was the wrong solution from the solution posted,