HP 50g Graphing Calculator - Manual (Page 598)

Page 18-31
When done, press @@@OK@@@. The results, as text and graph, are shown below:
Example 4 -- Determine a 90% confidence interval for the difference between
two proportions if sample 1 shows 20 successes out of 120 trials, and sample
2 shows 15 successes out of 100 trials.
Press ‚Ù—@@@OK@@@ to access the confidence interval feature in the
calculator. Press ˜˜˜@@@OK@@@ to select option 4. Z-INT: p1 – p2.. Enter
the following values:
When done, press @@@OK@@@. The results, as text and graph, are shown below: