Importing data into inference app

[mbeddo]

Hi Tim,

I appreciate your patience with me. Thanks.

But there are still issues in the inference app. Let me demonstrate:

1. Open Inference app
2. In the Home view, enter "RANDOM(100, 0, 1)" and store in D1. Enter "RANDOM(100, 0, 10)" and store in D2.
3. Switch to Symb view. Choose "Hypothesis Test", "Z-Test: mu1 - mu2", and "mu1 < mu2".
4. Switch to Num view. Import. Choose D1 for x1 and D2 for x2 sets. Then OK.
5. Look at the sigma values (sigma1 and sigma2) after the import.

The sigma1 0.2887 is correct (should be 1/sqrt(12)). The sigma2 0.2887 is incorrect (should be 10/sqrt(12) = 2.887).

One can always estimate the population standard deviations (and variances) for any sample size greater than 1, the issue is whether the sample size is large enough to trust the estimate. I'll admit that 6 values is too little, but surely 100 values is enough? The calculation for sigma2 is wrong (or at least is being displayed wrong), and with a two sample Z-test there is no requirement that the two population sigmas have to be the same.