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## Homework Statement

A high jumper knows from experience that she can clear a height of at least 1.78m once in 5 attempts. She also knows that she can clear a height of at least 1.65m on 7 out of 10 attempts.

Find to 3 dp the mean and standard deviation of the heights the jumper can reach

## Homework Equations

## The Attempt at a Solution

This is a question on an online tutorial. I work it out slightly differently and get different answers.

After rounding I get

mean of 1.700m

standard deviation of 0.091m

Would anyone be able to double check for me, it's using statistics tables so I'm not sure how to put all my working down. My exam is this coming week and I want to be sure I am using the tables correctly.

I suppose the main bits I would like to check are

[tex]\Phi[/tex](Z

_{1}) = 0.8

[tex]\Phi[/tex](-Z

_{2}) = 0.7

I get Z

_{1}= 0.8779 and Z

_{2}= -0.5534

This is where we get different answers. I use Neaves tables and do the "inverse normal function" to gain Z, where as he uses the "c.d.f of the standard normal distribution table", finds a probability valuse as close to 0.8 and 0.7 as possible and then takes the corresponding Z value.

Any help would be appreciated.

James