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MsLiz88
Apr 13, 2011, 12:04 PM
I am trying to find the percentage of people with a higher IQ then 111.

I have the equation, P(y>111) = P(z >.69)
At this point I believe I subtract 1 from a decimal number but I don't know what decimal number. It may come from a chart, but I guess I am not familiar with using the chart. After I do the subtraction I can find the percentage. Can anyone show me how to finish my problem?

Unknown008
Apr 13, 2011, 12:27 PM
It will all depend on what type of z-table you were given. If you have a right-tail end type table, then no, you directly look up the probability/percentage of 0.69 in your table.

If it's a left-tail end type table, you have to get the probability of:

P(z < 0.69)

since that's what you have in your table. Making a sketch tells you that you are looking for the complement of that probability, or that:

1 - P(z > 0.69) = P(z < 0.69)

You get P(z < 0.69) in your table, you can find P(z > 0.69). And hence find the percentage.

Other types of tables will require other approaches.