Statistics - GED Math

1. What is the range of $15$, $22$, $9$, $30$, $18$?

   $21$. Range is the greatest value minus the least: $30 - 9$.

2. What is the mode of a data set?

   The value that occurs most often. A set can have more than one mode, or none.

3. What is the mean of $4$, $8$, $10$ and $14$?

   $9$. The sum is $36$, and $36 \div 4 = 9$.

4. How do you find the mean of a data set?

   Add all the values and divide by the number of values.

5. Which measure of center is pulled more by an outlier, the mean or the median?

   The mean. The median depends only on the middle position, so it resists extreme values.

6. What is the median of $3$, $9$, $4$, $7$, $12$, $1$?

   $5.5$. In order: $1, 3, 4, 7, 9, 12$. The middle two are $4$ and $7$, and their mean is $5.5$.

7. How do you find the median of a data set with an even number of values?

   Put the values in order and take the mean of the two middle values.

8. Four test scores average $80$. What score on a fifth test raises the average to $82$?

   $90$. Five tests at $82$ total $410$, the first four total $320$, and $410 - 320 = 90$.

9. How do you calculate a weighted average?

   Multiply each value by its weight, add the products, and divide by the sum of the weights.

10. What is the mode of $2$, $5$, $5$, $7$, $8$, $8$, $8$?

    $8$. It appears three times, more than any other value.

11. A score of $70$ counts once and a score of $85$ counts twice. What is the weighted average?

    $80$. $\frac{70 + 2(85)}{3} = \frac{240}{3} = 80$.

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