chapter 2 stats

Question 1

What is the correct notation for x?

Answer 1

Sigma of x/n= x bar

Question 2

How do you calculate the mean of a grouped frequency table.

Answer 2

Sigma frequency X x/ sigma frequencies.

Question 3

When you are calculating median or quartile what should you do if you get a decimal?

Answer 3

Always round up.

Question 4

How to work out the variance?

Answer 4

The mean of the squares minus the square of the mean.

Question 5

What is the difference between variance and standard deviation.

Answer 5

standard deviation is the square root of the variance.

Question 6

What is the main difference between adding and subtracting when coding and then multiplying and dividing?

Answer 6

coding by adding and subtracting will only change averages.
BUT not measures of spread.

Coding by multiplying and dividing will change both averages and spread.

Question 7

How do you calculate the mean when you have two different means and the number of observations in each of them?

Answer 7

Multiply the mean by the number of observations to find sigma x.
Then add the sigma x of both and add the number of observations of both and divide them

Question 8

How to calculate the median?

Answer 8

n/2 if it is decimal round up and this is the corresponding term

If it is whole number use this and number above to find midpoint.

Question 9

Pro and con for mode?

Answer 9

Pro- can be used for both qualitative and quantitative data.

Con- There is no mode if each value appears with the same frequency

Question 10

Pro and con for median?

Answer 10

Pro- unaffected by anomaly or outlier.

Con- it does not use every data value in the set

Question 11

Pro and con for mean?

Answer 11

Pro- all values within the data set are used.

Con- can be skewed by anomalies.

Question 12

How to work out lower quartile and upper quartile?

Answer 12

Lower quartile is n/4 (if it is a decimal round up, if it is whole use that number and the following to find midpoint.)

Upper quartile 3n/4 (if it is a decimal round up, if it is whole use that number and the following to find midpoint.)

Question 13

How to calculate the mean of a grouped frequency table?

Answer 13

frequency times x / total frequency.

Question 14

What is important when working with grouped frequency tables?

Answer 14

Think about the lower and upper bounds if it has been rounded.

Question 15

What is the formula for linear interpolation?

Answer 15

Lower Bound + ( depth intro group/ group frequency) x Class width of group.

Question 16

When do you round for group tables and where do you not?

Answer 16

For continuous data you use rounding for discrete you do not.

Question 17

What does the IQR do?

Answer 17

It measures the spread of the middle 50% of data.

Question 18

How do you calculate variance?

Answer 18

The mean of the squares - the mean squared

Question 19

How do you calculate standard deviation?

Question 20

What is an alternative way of calculating standard deviation?

Answer 20

square root of sxx over n

Question 21

What is standard deviation?

Answer 21

It is a measure of spread and looks at the average distance of each data point from the mean.

Question 22

What is the difference between standard deviation and variance?

Answer 22

Standard deviation is the root of the variance.

Question 23

What must you do when finding the standard deviation of grouped frequency?

Answer 23

Use the midpoint as the x value.

Question 24

What is one standard deviation above the mean?

Answer 24

mean + standard deviation.

Question 25

Why is coding useful?

Answer 25

if data in a set is particularly large they can be made simpler.

Question 26

What impact will coding have on measures of spread and measures of average if you add or subtract.

Answer 26

For measures of spread it will have no impact.

For averages

Question 27

What is different when encoding measures of spread?

Answer 27

You must only divide or multiply you do not need to add or subtract to reverse.

Question 28

How could you use sxx In data?

Answer 28

Divide by n and square root to find standard deviation.