Question 1185718
Here's how to find the value of *c*:

1.  **Understand the problem:** We're given the probability that a standard normal variable *z* is *greater* than *c*. We need to find the corresponding *c* value.

2.  **Convert to a left-tail probability:** Most statistical tables and calculators give probabilities to the *left* of a z-score.  Since the total probability under the normal curve is 1, we can find the probability to the *left* of *c*:

    P(z < c) = 1 - P(z > c)
    P(z < c) = 1 - 0.6892
    P(z < c) = 0.3108

3.  **Find the z-score:** Now we need to find the z-score that corresponds to a cumulative probability of 0.3108. You can use a standard normal (z) table or a statistical calculator for this. Look up the probability closest to 0.3108 in the table's body and find the corresponding z-score.

    *   If using a calculator, you can use the inverse cumulative distribution function (often called `norm.ppf` or similar).

The z-score you find will be your value of *c*.  It will be a negative value since the probability is less than 0.5.

c ≈ -0.49