Calculated Confidence Intervals

[RL8500]

How does one do a z or test/confidence interval without the standard deviation? (given only the mean/proportion and sample size)

This can be done on other calculators, like the TI-84, and I wonder how it can be done here.

Thanks.

[ftneek]

I believe you can use the Inference app for this.

Method: confidence interval
Type: Z-Int: 1 π
Press [num]
x - success count (if given proportion of successes, p*n approx = x)
n - sample size
C - confidence level
Then press the Calc key on screen. Lower/Upper is the CI.

Alternatively you can use the command ConfZ1prop(SuccCount, SampSize, ConfLevel), which returns a list of 4 values: {Lower critical value, lower bound, upper bound, calculated proportion}.