Intro

Question 1

What is a measure of central tendency?

Answer 1

A measure that gives a general idea of the centre of the distribution of the data

Question 2

If you have nominal data, what measure would you use to find the central tendency?

Answer 2

Mode

Question 3

Advantage and 2 disadvantages of mode?

Answer 3

Not affected by extremely high or low values (outliers)

Dis:

• some distributions have no mode (uniform dist.)
• ignores distribution of observations - non modal values therefore have no weight

Question 4

Problems with the mode? (2)

Answer 4

Some distributions have more than one mode (bimodal)

With OIR data the modal score may not be central to the distribution as a whole

Question 5

Four types of measurement of data?

Answer 5

Nominal
Ordinal
Interval
Ratio

NOIR

Question 6

What is nominal data (3) and example?

Answer 6

Observations of a qualitative variable are measured and recorded as labels or names.
Data is classified into categories and can’t be sorted into an order.
Only mathematical operation permitted is classifying and counting.

Example: gender

Question 7

2 characteristics of nominal data?

Answer 7

Mutually exclusive

Exhaustive (each object must appear in one of the categories)

Question 8

What is ordinal data (2) and example?

Answer 8

Data oranges in an order, but differences between values are meaningless.
Most advanced mathematical operation on this data is ranking of categories.

Eg. Level of education:
GCSE
A level
Degree

Question 9

What is interval data (2) and example?

Answer 9

Meaningful amounts of differences between data values can be determined.
No absolute zero score

Eg. Temperature in Celsius or shoe size

Question 10

Why can’t you say ‘100 degrees Celsius is twice as hot as 50 degrees Celsius’?

Answer 10

Because 100 is not twice as hot as 50, since 0 doesn’t represent absolute zero (doesn’t represent the absence of heat, only the freezing point of water)

Question 11

What is ratio data and example?

Answer 11

Extension of the interval data to include an inherent zero starting point.

Eg. Weight, age, temperature in kelvin

Question 12

Advantages of median? (3)

Answer 12

Not affected by outliers
Unique median for each data set
Can be computed for OI and R data

Question 13

What is a parameter?

Answer 13

A measurable characteristic of a population

Question 14

What is a statistic?

Answer 14

A measurable characteristic of a sample

Question 15

Characteristics of mean? (4+ formula)

Answer 15

Unique (only one per dataset)
Requires interval or ratio data
Every single score affects it
Sum of deviations from mean is always zero

Σ(xi - xbar) = 0

Question 16

What is the least squares principle? (1+formula)

Answer 16

If the difference between the mean value and the scores are squared and then added, the resultant sum is the minimum possible.

Σ(xi - xbar)^2 = min

Question 17

Disadvantage of mean?

Answer 17

Affected by extreme values (outliers)

Question 18

Three common data shapes?

Answer 18

Mean = median - symmetrical dist.

Mean > median - positive skew

Mean < median - negative skew

Question 19

Coefficient of skewness equation?

Answer 19

sk = (3(xbar - median))/s

s is standard deviation

Question 20

2 equations for frequency distribution?

Answer 20

2^k > N (k is no. of classes)
Class interval determined by:

i = (H-L)/k THEN ROUND UP

Question 21

Upper and lower limit of frequency distribution classes?

Answer 21

Must include all values in data

Question 22

Histogram axis labels?

Answer 22

X - class intervals
Y - class frequencies

BARS TOUCH

Question 23

What is a frequency polygon?

Answer 23

A histogram with straight lines joining the midpoint of adjacent frequency bars

Question 24

If there is a weird column on the left hand side of a stem and leaf diagram what is it?

Answer 24

Cumulative frequency

Question 25

What goes on the axis of a bar chart?

Answer 25

X - class intervals
Y - class frequencies

Question 26

What is a line chart good for showing?

Answer 26

Change over time