Question

Suppose Z follows the standard normal distribution. Calculate the probability: (a) P(z <= 1.04) Option a) 0.855 Option b) 0.151 Option c) 0.396 Option d) 0.709

Answer 1

Answer: 0.855

Step-by-step explanation

Use the Z table found in the back of your stats textbook. Locate the row that starts with "1.0", and the column that has "0.04" at the top. The intersection of those would produce the approximate value 0.85083

That value is somewhat close to 0.855; there's some rounding error going on with the value 0.855 that your teacher provided.

Another option is to use a TI83 or TI84. Press the button labeled "2ND". Then press the VARS key. Scroll down to normalCDF.

The input template is: normalCDF(lower, upper, mu, sigma)

In this case:

• lower = -9999 = some really small number to represent "negative infinity".
• upper = 1.04
• mu = 0 = mean
• sigma = 1 = standard deviation

The TI83 or TI84 calculator will then produce an output of roughly 0.8508300289

The "0.85083" portion matches up perfectly with what we got from the table.