Suppose we test a new device in 20 healthy volunteers and measure the change in their heart rate. The mean was 10 and the standard deviation was 5. Compute the 90% confidence interval for , the population mean change in the heart rate.

Which of the following are true about the interval you calculated and the calculations used?

1. P (calculated interval is correct) = 0.90
2. P (calculated interval is not correct) = 0.10
3. The t-values used to calculate the interval were+1.729
4. The z-values used to calculate the interval were+1.64
5. If we took another 20 volunteers and calculated another interval, we would expect to get the exact same numerical values.
6. The formula we used to calculate our interval gives us the right answer (contains) 90% of the time.
7. If we had used a 95% confidence level, the width of the interval would have been smaller.