Data representation & Regression and Correlation

Question 1

What do we need on a box plot?

Answer 1

1. Minimum and maximum value
2. Median
3. Upper and lower quartile (Q1 and Q3)
4. Outliers represented as crosses

Question 2

How do we find outlier boundaries?

Answer 2

Q1-1.5xIQR
Q3+1.5xIQR

Question 3

What kind of data do we use for histograms?

Answer 3

Continuous data

Question 4

What equation do we need to remember with histograms?

Answer 4

Kf=cw x fd

Question 5

How do we find frequency density with a histogram?

Answer 5

Frequency/ class width

Question 6

What is the area of a histogram equal to?

Answer 6

Frequency x k
(you must find out what k is in the question)

Question 7

What do we do when we are comparing sets of data?

Answer 7

1. Compare a measure of location (median, mean)
2. Compare a measure of spread (variance,standard deviation)
3. Pu them into context

Question 8

What is the correlation coefficient?

Answer 8

It is a value which measures the strength and positivity/negativity of correlation on scatter graphs.

Question 9

What values is the correlation coefficient between?

Answer 9

-1≤ r ≤ 1

Question 10

What value is r when there is no correlation and what would that look like on a scatter graph?

Answer 10

0

Question 11

What would a scatter graph with a positive correlation look like?

Answer 11

Question 12

What would a scatter graph with a negativecorrelation look like?

Answer 12

Question 13

What is a regression line and what is its formula?

Answer 13

Line of best fit
comes in the form y=mx+c

Question 14

What is interpolation?

Answer 14

Estimating inside the data range

Question 15

What is extrapolation?

Answer 15

Estimating outside the data range

Question 16

Why is interpolation better than extrapolation?

Answer 16

Because it is more reliable.

Question 17

What are the advantages and disadvantages of using box plots?

Answer 17

+Highlights outliers
+Makes it easy to compare data sets
-Data is grouped into only 4 categories so some detailed analysis isn’t possible

Question 18

What are the advantages and disadvantages of using histograms?

Answer 18

+Clearly shows shape of distribution
-Doesn’t always highlight outliers
-Not easy to estimate Q1,Q2,Q3

Question 19

What are the advantages and disadvantages of using cumulative frequency curves?

Answer 19

+Easy to find the five number summary (Q1,median, etc)
-Doesn’t always hgihlight outliers
-If interval boundaries aren’t shown. the degree of detail is not clear.

Question 20

What does it mean when a box plot is positively skewed and what does this look like?

Answer 20

The median is closer to the LQ than the UQ

Question 21

What does it mean when a box plot is negatively skewed and what does this look like?

Answer 21

The median is closer to the UQ than the LQ