The total weekly claim amount is normally distributed with mean 1,000 and standard deviation 200 dollars.
Calculate the probability that it is between 850 and 1,300 dollars.
Exam P gives you one table, the standard normal, on screen under the Exhibit button. Here it is, with a lookup that finds the probability or the z and shows where to read it.
From the table
0.9750
From exact z: 0.9750
The first decimal of z is down the side, the second across the top. Tap a value to look it up.
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| P(Z < z) | 0.750 | 0.800 | 0.850 | 0.900 | 0.950 | 0.975 | 0.990 | 0.995 |
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| z | 0.6745 | 0.8416 | 1.0364 | 1.2816 | 1.6449 | 1.9600 | 2.3263 | 2.5758 |
| On the exam | On screen under Exhibit; you may not bring your own copy |
|---|---|
| What it gives | P(Z < z) for z from 0.00 to 3.99, to four decimals |
| Answer choices | Computed from exact normal values: pick the closest |
z = 1.645 leaves 5% in the upper tail, 1.960 leaves 2.5% and 2.326 leaves 1%. The two-sided 95% range is the mean plus or minus 1.960 standard deviations.
SOA's notes to the table say the answer choices are computed from exact normal values, so rounding z to the table can land slightly off them. Choose the closest answer. The lookup shows both the table reading and the exact value.
The total weekly claim amount is normally distributed with mean 1,000 and standard deviation 200 dollars.
Calculate the probability that it is between 850 and 1,300 dollars.
An insurer has a portfolio of claims. Each of 100 independent claims has mean 250 and standard deviation 80 dollars.
Using the normal approximation, calculate the probability that the total of the 100 claims exceeds 26,000.
Yes. A standard normal table is shown on screen under the Exhibit button, so you may not bring your own copy.
SOA's notes say the answer choices use exact normal values and that rounding to the table may give a slightly different answer. Round z to two decimals and choose the closest answer.
1.645, since P(Z < 1.645) = 0.95. For a two-sided 95% range, use 1.960.