week 2- data analysis

Question 1

histogram and ogive

Answer 1

x y
histogram intervals frequency
ogive (ungrouped
measurement grouped) CF
top of interval

Question 2

histogram interpretation
- the modal class

Answer 2

the tallest column

Question 3

histogram interpretation
- skewness

Answer 3

• graph lean to the right = negative skew
• graph lean to the left = positive skew

Question 4

histogram interpretation
- outliers

Answer 4

data that is unusual

Question 5

draw the ogive

Answer 5

x axis - top of interval
y axis - cumulative frequency

Question 6

median formula - ungrouped data

Answer 6

(n+1)/2

Question 7

median formula - grouped data

Answer 7

(n+1) x 50%

Question 8

measures of average compared
- the mode or the median can give a better average than the mean when the data is skewed
positive

Answer 8

the mode > median > mean

Question 9

measures of average compared
normal

Answer 9

‘perfect’ mean=median=mode

Question 10

measures of average compared
negative

Answer 10

the mode < median < mean

Question 11

range formula

Answer 11

highest value - lowest value

Question 12

coefficient of variation
formula

Answer 12

this is standard deviation expresses as a % of the mean
standard deviation/ mean x 100

Question 13

why calculate the coefficient of variation

Answer 13

is useful for comparing the spread of different data sets (e.g. long bolts of approximately. 16 cm with short one approx. 16mm)

Question 14

interquartile range formula

Answer 14

Q3-Q1

that is the range for the mid 50% of data

Question 15

quartile deviation formula

Answer 15

(Q3-Q1)/2

Question 16

what is standard deviation

Answer 16

• is a measure of spread from the mean
• it includes all data and is used in statistical analysis
• can be affected by skewed data and is affected by open classes

Question 17

what is interquartile range

Answer 17

• measures middle 50% of data and is usually used with median
• can be useful when data is skewed or where there are outliers
• disregards bottom and top 25% of data

Question 18

how to work out Q1

Answer 18

(n+1) x 25%

Question 19

how to work out Q2

Answer 19

median
or
(n+1) x 50%

Question 20

how to work out Q3

Answer 20

(n+1) x 75%

Question 21

how to work out variance

Answer 21

standard deviation to the power of 2

Question 22

to draw graphs remember that:

Answer 22

histogram uses: x axis = intervals and y axis = frequency (BAR CHART)

ogive uses: x axis = top of interval and y axis = cumulative frequency (LINE CHART)

Question 23

what does this symbol mean
~
-

Answer 23

approx equal to

Question 24

variance formula

Answer 24

standard deviation squared