MGQ 201WEEK 4

VICTORIA LOJACONO

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Chapter 3 HomeworkQuestion 1 NotesMean: average

Median: middle number

Mode: number that occurs most often

If mean > median then it’s right skewed

If mean < median then it’s left skewed

If the mean and median are approximately equal, it is symmetricalApproximately equal means a difference of less than 1

Do this in excel!

Question 1

Question 2 NotesWeighted Average

Step 1: Find x*f (number of products * frequency)

Step 2: Sum the frequencies

Step 3: Sum the products (x*f)

Step 4: Sum of products divided by sum of the frequencies

Question 2*Do this in excel

Question 3Note: When outliers are present in the data, the median is often the best choice because it is unaffected by them. Otherwise, either the mean or the median are both accurate measures of central tendency. When the data is categorical, the mode is the best choice when it exists.

Question 3 Continued

Chapter 4 NotesRange = highest value – lowest value

Population variance = sum of squared given values – (the sum of the original values squared/number of values)

Number of values

Standard deviation = square root of the variance

Question 4*see excel

Question 5 NotesCoefficient of variation = (sample standard deviation / sample mean) * 100

Use =STDEV.S( formula in excel to find the sample standard deviation

The set with the larger coefficient of variation has more variability (or less consistency)

Question 5

Question 6 NotesZ score = (x – average) / sample standard deviation

Use excel to calculate the standard deviation

Question 6

Question 7 Notes Calculate mean of sample data:

1. Find midpoint (x) for each class2. Multiply each midpoint by the appropriate frequency (x*f)3. Sum (x*f)4. Sum frequencies5. Sample mean = sum (x*f) / sum frequencies

Calculate standard deviation of sample data1.Find the midpoint – sample mean for each class2.Take that answer and square it3.Then multiply it by the appropriate frequency4.Add the answers for each class together5.Take that number divided by (sum of original frequencies – 1)6.Take the square root of that number

Question 7

Question 8 NotesP = percentilen = number of values

Take the number you get for i and round up.

That number corresponds to the number in the data set.

Example: If i is 2 and the data set (in order from smallest to largest) is:

5 8 10 12

Then the answer is 8Because 8 is the 2nd number in the set

Question 8*Use excel to order the numbers

Question 9 Notes

You must order the numbers first

Follow the rounding rules.

Question 9*Use excel to order the numbers

Question 10 NotesIn Excel:

First quartile: =QUARTILE.INC(range,1)

Second quartile: =QUARTILE.INC(range,2)

Third quartile: =QUARTILE.INC(range,3)

Inner quartile range = Q3 – Q1

Question 10

Question 11 Notes Sample covariance:

1. Find the mean of the set of x and the set of y

2. subtract each value from each set from the mean

3. multiply the corresponding answers for #2 [(x-mean of x)*(y-mean of y)]

4. sum those values

5. sum/(N-1)

Sample correlation coefficient:

1. use STDEV.S( formula to find the sample standard deviation of each original x and y set

2. use formula: sample covariance / (stdev of x)*(stdev of y)

Relationship between x and y

Measured by how close the correlation coefficient is to +1 or -1

Correlation coefficient of +1 = positive linear relationship

Correlation coefficient of -1 = negative linear relationship

Question 11

RemindersStats quiz due 9/28