Lec 2

Question 1

Mode

Answer 1

❖ It is the value which occurs most frequently.

Question 2

Data distribution with one mode is called

Answer 2

Unimodal

Question 3

If all values are different there is no mode or called

Answer 3

Non modal

Question 4

Sometimes, there are more than one mode: two modes is called
…………..; more than two is called
……….. distribution.

Answer 4

Bimodal
Multimodal

Question 5

Normally, the mode is used for ………………where we wish to
know which is the most common category

Answer 5

Categorical data

Question 6

What is the advantage of the mode

Answer 6

Sometimes gives a clue about the etiology of the disease.

Question 7

Disadvantages of mode

Answer 7

With small number of observations, there may be no mode
✓ It is less amenable to tests of statistical significance

Question 8

This is the mode value for the data set
0,3,4,5,7,7,7,7,7,8,10,10

Answer 8

7

Question 9

The Mean

Answer 9

Mean It is the average of the data or the sum of all values of
a set of observations divided by the number of these observations.

Question 10

most popular and well known
measure of central tendency

Answer 10

The mean an average

Question 11

Mean used with

Answer 11

Discrete and continuous data

Question 12

Advantages of mean

Answer 12

Uniqueness: For a given set of data there is one and only
one mean, it is single value.
✓ Simple to compute.
✓ All values are included.

Question 13

Disadvantages of mean

Answer 13

The main disadvantage of mean is the presence of extreme
values, i.e. very high or very low values.

Question 14

The Median (50th percentile)

Answer 14

The median of a data set is the value that lies exactly in the middle.
To calculate the median:

Question 15

The value of the median will be

Answer 15

value in the middle for odd
number and
the average of the two values for even numbers.

Question 16

Advantages of median:
.

Answer 16

Advantages of median:
✓ It is a single value,
simple, easy to compute easy to
understand,
unaffected by extreme values.

Question 17

Disadvantages of median

Answer 17

It provides no information about all values (observations).
✓ It is less amenable than the mean to tests of statistical
significance.

Question 18

Mode described

Answer 18

Qualitative categorical data

Question 19

Mean is ……… value
Median is ……..value
Mode is……….value

Answer 19

Single (unique)
Single (unique)
Sometimes it’s not unique

Question 20

quintile

Answer 20

statistical value of a data set that represents 20% of
a given population.
✓ The first quintile represents the lowest fifth of the data (1 -20%)
✓ The second quintile represents the second fifth (21% - 40%) and
so on.

Question 21

tertiles

Answer 21

❖ A population split into three equal parts is divided into

Question 22

One of the most common metrics in statistical analysis, the
………., is actually just the result of dividing a population into
…………

Answer 22

Median
Two quantiles

Question 23

Quartiles

Answer 23

These are the observations in an array that divide the distribution
into four equal parts
❖ 1st (lower Quartile): the value below which 25 of observations lie
in an ordered array.
❖ 2nd quartile = Median = 50th percentile
❖ Upper Quartile = 75th percentile
❖ Interquartile Range: is the middle 50 % of all observations (From
25-75)

Question 24

Median result from

Answer 24

Two quantile
Second quartile
50 th percentile

Question 25

Centiles

Answer 25

Those values, in a series of observations arranged in ascending order of magnitude, which divide the distribution into 100 equal parts.

Question 26

Define the range It considers important ⁉️ Should be used

Answer 26

The range is the difference between the largest and the smallest observation in the data. ❖ It is an important measurement However, they do not give much indication of the spread of observations about the mean. ❖ Should be used in conjunction with other measures of variability.

Question 27

Advantages and disadvantages of the range

Answer 27

Advantages ✓ Simple to calculate ✓ Easy to understand Disadvantages ✓ It neglect all values in the center and depend on the extreme value, and extreme value are dependent on sample size. ✓ It is not based on all observations. ✓ It is not amenable for further mathematic treatment.

Question 28

Variance

Answer 28

The average of sum of squares of the deviation from the mean

Question 29

The standard deviation

Answer 29

The standard deviation measured the variability between observations in the sample or the population from the mean of that sample or that population.

Question 30

Standard error of the mean

Answer 30

It measures the variability or dispersion of the sample mean from population mean. ❖ It is used to estimate the population mean, and to estimate differences between populations means.

Question 31

Coefficient of variation (CV)

Answer 31

❖ It has no unit.

Question 32

Coefficient of variation used to compare It measure

Answer 32

It is used to compare dispersion in two sets of data especially when the units are different. relative rather than absolute variation. in consideration all values in the set.

Question 33

Variance can never be

Answer 33

A negative value

Question 34

The problem with the variance is the

Answer 34

Squared unit

Question 35

Standard deviation it is …….. Unit of standard deviation …….

Answer 35

Square root of the variance Unit not squared