3 high-school stats Qs: What is the area under the standard normal curve between z = -1.28 and z = 1.28?

[robinyashed]

Doing high school statistics questions here's of how far I got. But I'm confused of how it played out?

1. What is the area under the standard normal curve between z = -1.28 and z = 1.28? (4dp)

2. What is the z-value that gives the left hand tail area equal to 0.0102? (2dp)

3. What is the absolute value of z such that the total area under the standard normal curve between –z and +z will be 0.7924? (2dp)

 

[Dr.Peterson]

You haven't shown any work, and that's especially important for this kind of problem, because how to do it depends somewhat on what you have been given.

Often these are done using a standard normal distribution table. Wikipedia shows three different kinds of tables (two of which I have seen in textbooks; I get the impression that the second type is the current standard for textbooks, but maybe not everywhere). So I can't show you how to do it without being sure what kind of table you have, if any. Or you might be expected to do it with software; if so, what kind?

Does your textbook give examples of this sort of question, worked out? (I'd certainly expect it to.)