U Can: Statistics For Dummies

Appendix

Tables for Reference

This appendix includes tables for finding probabilities and/or critical values for the three distributions used in this book: the Z-distribution (standard normal), the t-distribution, and the binomial distribution.

The Z-Table

Table A-1 shows less-than-or-equal-to probabilities for the Z-distribution; that is, p(Z ≤ z) for a given z-value. (See Chapter 10 for calculating z-values for a normal distribution; see Chapter 12 for calculating z-values for a sampling distribution.) To use Table A-1, do the following:

1. Determine the z-value for your particular problem.

   The z-value should have one leading digit before the decimal point (positive, negative, or zero) and two digits after the decimal point; for example, z = 1.28, –2.69, or 0.13.

2. Find the row of the table corresponding to the leading digit and first digit after the decimal point.

   For example, if your z-value is 1.28, look in the “1.2” row; if z = –1.28, look in the “–1.2” row.

3. Find the column corresponding to the second digit after the decimal point.

   For example, if your z-value is 1.28 or –1.28, look in the “0.08” column.

4. Intersect the row and column from Steps 2 and 3.

   This number is the probability that Z is less than or equal to your z-value. In other words, you’ve found p(Z ≤ z). For example, if z = 1.28, you see p(Z ≤ 1.28) = 0.8997. For z = –1.28, you see p(Z ≤ –1.28) = 0.1003.

Table A-1 The Z-Table

The t-Table

Table A-2 shows right-tail probabilities for selected ...