vcaa 2009 3.d exam 2

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how do you do this?

[BubbleWrapMan]

Notice that the two values are exactly the same distance from the mean, this implies that 0.5% lie below this interval and 0.5% lie above.

So, the probability of a ball being less than 68.4 is 0.995, so you can use inverse normal on Pr(Z < 1.4/sigma) = 0.995 and solve for sigma

[dfgjgddjidfg]

thanks mate