Given that z is a standard normal random variable, compute the following probabilities (to 4 decimals).

P(z -1.0)


P(z -1.0)


P(z -1.5)


P(z -2.5)


P(-3 < z 0)

1 answer

To find the probabilities for a standard normal random variable, we use the Z-table (also known as the standard normal table) which provides the area (probability) to the left of a given Z-score.

Here's the link to a Z-table for your reference: http://www.z-table.com/

Now, we will use the Z-table to find the probabilities for each given Z-score.

1. P(z < -1.0): From the Z-table, the probability is 0.1587.

2. P(z > -1.0): Since the area under the entire curve sums up to 1, P(z > -1.0) = 1 - P(z < -1.0) = 1 - 0.1587 = 0.8413.

3. P(z > -1.5): From the Z-table, P(z < -1.5) = 0.0668. Therefore, P(z > -1.5) = 1 - 0.0668 = 0.9332.

4. P(z > -2.5): From the Z-table, P(z < -2.5) = 0.0062. Therefore, P(z > -2.5) = 1 - 0.0062 = 0.9938.

5. P(-3 < z < 0): Here, we need to find the probability between two Z-scores. P(-3 < z < 0) = P(z < 0) - P(z < -3). From the Z-table, P(z < 0) = 0.5000 and P(z < -3) = 0.0013. Therefore, P(-3 < z < 0) = 0.5000 - 0.0013 = 0.4987.

So, the requested probabilities are:

P(z < -1.0) = 0.1587
P(z > -1.0) = 0.8413
P(z > -1.5) = 0.9332
P(z > -2.5) = 0.9938
P(-3 < z < 0) = 0.4987