Week 2 - Jan 20

Question 1

What is the calculation for median?

Answer 1

(N+1)/2= the position in which the number exists

For example: 1, 3, 4, 5, 9 the median is 4.

Question 2

How to calculate the median when there are two middle numbers?

Answer 2

N/2=Median

Example: 1, 2, 2, 4, 6, 9 the median is calculated as 2+4/2=3, the median is 3

Question 3

If the numbers have one significant outlier, should you use mean and median?

Answer 3

Median as it will likely give a more realistic picture.

Question 4

What is the range and how to find it in excel?

Answer 4

The largest number minus the smaller number.

In excel use =max(a1:a7) and =min(a1:a7) then subtract the two in a third cell. Example =max(a1:a7)-min(a1:a7)

Question 5

How to calculate variance?

Answer 5

Mean-every data item=variance

Example: what is the variance of 1, 2, 3 days? Calculate the mean which is (1+2+3)/3=2 then you take 1 and subtract the mean, take 2 and subtract the mean and 3 and subtract the mean which looks like
1-2=1
2-2=0
3-2=1
The variance is 1 days^2 (days squared).

Variance is always represented as squared.

Excel uses =var.s (for a sample) or =var.p (for population)

Question 6

How to calculate standard deviation?

Answer 6

The square root of the variance.

Excel uses =sqrt(insert number) then =stdev.p(number range) for sample standard deviation or =stdev.p(number range) for population standard deviation. Standard deviation uses the same measurement as the data where as variance is always squared.

Question 7

What is the formula for skewed?

Answer 7

Skewness=(3(mean-median))/Standard Deviation

Excel uses =SKEW(number range)

Question 8

How to tell if your data is skewed?

Answer 8

If the mean is larger than the median, then the data is skewed right.
If the mean is smaller than the median, then the data is skewed left.

Question 9

What are the three numbers of six sigma?

Answer 9

0.68 or SD1 (standard deviation)
0.95 or SD2
0.997 or SD3

Question 10

How do you get to 6 sigma?

Answer 10

Standard Deviation is Sigma so 3SD above the mean plus 3 SD below the mean adds to 6 Sigma.

Question 11

What is the empirical rule?

Answer 11

Six sigma

Question 12

How to calculate the empirical rule?

Answer 12

Upper value and lower value equals the empirical rule or range between which the numbers fall.

With a meaning of 600, an SD of 10, what is the interval needed to hold 95% of data?
95% is SD2 therefore:
Upper value is 600+10+10=620
Lower value is 600-10-10=580
Answer is 580 to 620.

Question 13

What is the calculation for Chebyshev?

Answer 13

Percent of data=1-1/standard deviation

Question 14

What is the calculation for coefficient variation?

Answer 14

Coefficient variation=(SD/mean)x100

Question 15

How is standard deviation calculated?

Answer 15

The square root of variance.

Variance is found by subtracting every data item from the mean and totalling the totals.