The number of cd's sold by Dave's Discs for the last 6 days are given in the table:

**The mean is the average of the number of discs
sold. **

So we need to sum up all of the CD's sold and then divide by 6, since
there are 6 days:

**We need to list the numbers in numeric order:**

**10, 10, 10, 15, 15, 18**

If we pick 10 (the third one) for our median we have two values below it and three above it. If we pick 15 (the first one) for our median then we have three values below it and two above it. So neither of those values are the median. This does not mean we don't have a median.

Note how there is an even number of values listed. If that
is the case, we need to draw a line down the middle of the list and take
the mean of the two numbers next to that line.

**10, 10, 10 | 15, 15, 18**

The mean of 10 and 15 is

It helps to list the numbers in order to find the mode.

**10, 10, 10,
15, 15, 18**

Note how 10 occurs three times, which is the value that occurs the most.

**10 is the mode.**

A student received scores of 92, 83, and 71 on three quizzes. If tests count twice as much as quizzes, what is the lowest score that the student can get on the next test to achieve a mean of at least 80?

Keep in mind that the test score counts twice instead of of time.
So when we set this up we need to make sure that we notate that properly.

***Solve for x (missing
test)**

***Inverse of div. by 5 is mult. by 5**

***Inverse of add 246 is sub. 246**

Find the range and standard deviation of the list of scores that were made by a football team during a season:

7, 21, 21, 17, 17, 14, 7, 0

I don't know about you, but I find it easier to work with a group of
numbers like this when they are in chronological order. Let's put
them in order from lowest to highest: 0, 7, 7, 14, 17, 17, 21, 21.

**Let's find the range.** What
do you think it is?

Looking at the difference between the largest value, which is 21 and
the smallest value, which is 0, it looks like **the range is 21. **

Now lets tackle the **standard deviation**.

So we need to sum up all of the values and then divide by 8, since
there are 8 numbers:

***Add numerator**

***Divide by 8**

**Step 2: Find the difference between the mean and each
separate value of the data set,**

**AND**

**Step 3: Square each difference found in step 2,**

**AND**

**Step 4: Add up all of the squared values found in
step 3.**

Find the mean of the frequency distribution.

As requested, I'm going to use the frequency distribution to set up
my mean formula. Instead repeating numbers in my sum, I'm going to
indicate a repetition by taking that value times the number of times it
occurs in the list. For example, 20 occurs 10 times. Instead
of writing it out 10 times in my sum, I will find 20(10) which is the equivalent.

***calculate numerator**

***divide**

Last revised on August 7, 2011 by Kim Seward.

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