6.3

1: Normal curves are symmetrical, and 30 is the mean of this distribution.

3: The middle of the curve is at z ⚌ 0.

14: This problem can be done like #5, or it can be reasoned out with no calculations or table.

16: Look for .052 inside the z table to find what z value has this amount to the left of it in the normal curve.

19: Look for .92 inside the z table to find what z value has this amount to the left of it (and .08 to the right of it) in the normal curve.

23: A range of .98 centered at .50 has half of .98 on each side of .50, so it goes from .50 – .49 to .50 + 49.

29: For (a), convert 36 months to a z score and look it up in the table, and for (b), find what z score has 10% of the normal curve to the left of it, and work backward from there.

36: Use the same method as for #5.

1: Normal distributions are symmetrical.

3: Only a little bit of the curve lies to the left of z, and most of it lies to the right.

9: Do the steps for normal problems: Find the z scores, sketch them on the curve and shade between them, find the shaded area by getting the areas (from the table) and subtracting.

14: See the bottom of the chart for z values that are off the chart (like z ＝ 4 in this case).

16: Convert 5.2% to a decimal so you can look it up in the table.

19: Look up the complement of 8% to find the area above 8%.

23: The middle 98% of the curve is 49% below the middle and 49% above the middle.

29: For (a), find the percentage for x ＝ 36 months (see 6-B), and for (b), find the number of months x for the bottom 10% (see 6-C).

36: Convert 7200 and 8900 to z scores so you can look up their percentages.

1: Normal distributions are symmetrical about the mean.

16: Convert 5.2% to a decimal so you can find it inside the table.

19: Look up the complement of 8% to find the area above 8%.

23: The middle 98% of the curve is 49% below the middle and 49% above the middle.

3: Only 5% of the area under the curve lies to the left of z, and the rest of it lies to the right.

14: See below the table for z values that are off the chart (like z ＝ 4 in this case).

29: For (a), find the percentage for x ＝ 36 months (see 6-B), and for (b), find the number of months x for the bottom 10% (see 6-C).

36: Convert 7200 and 8900 to z scores so you can look up their percentages.