PRELIM LEC 2 (2): DESCRIPTIVE STATISTICS

Question 1

Deals with the collection and presentation of data and collection of summarizing values to describe its group characteristics

Answer 1

DESCRIPTIVE STATISTICS

Question 2

✔ central thread of any activity
✔ Understanding the nature of data is most fundamental for proper and effective use of statistical skills

Answer 2

DATA

Question 3

2 TYPES OF DATA

Answer 3

ACCORDING TO SOURCE
ACCORDING TO FUNCTIONAL RELATIONSHIP

Question 4

2 TYPES OF DATA ACCORDING TO SOURCE

Answer 4

Primary Data
Secondary Data

Question 5

interview, registration, experiment, questionnaire, etc

Answer 5

PRIMARY DATA

Question 6

book, journal, newpaper, thesis, dissertation, etc.

Answer 6

SECONDARY DATA

Question 7

2 TYPES OF DATA ACCORDING TO FUNCTIONAL RELATIONSHIP

Answer 7

Independent Data
Dependent Data

Question 8

refers to any controlling data

Answer 8

Independent Data

Question 9

refers to any data that is affected by controlling data

Answer 9

Dependent Data

Question 10

METHODS OF COLLECTING DATA

Answer 10

o Objective Methods
o Subjective Methods
o Use of Existing Records

Question 11

METHODS IN PRESENTING DATA

Answer 11

o Textual
o Tabular
o Graphical

Question 12

summarizes a data set by giving a “typical value” within the range of the data values that describes its location relative to entire data set

Answer 12

Measure of Location

Question 13

MIN is the smallest value in the data set while MAX is the largest value in the data set

Answer 13

Minimum and Maximum

Question 14

it is the average of the data

Answer 14

Mean

Question 15

Properties of the Mean

Answer 15

o Uniqueness
o Simplicity
o Affected by extreme values

Question 16

Divides the observations into two equal parts
o If n is odd, the median is the middle number.
o If n is even, the median is the average of the 2 middle number

Answer 16

Median

Question 17

Value that occurs most often

Answer 17

Mode

Question 18

A data set that has only one value that occurs with the greatest frequency

Answer 18

Unimodal

Question 19

If a data set has two values that occur with the same greatest frequency, both values are mode

Answer 19

Bimodal

Question 20

If a data set has more than two values that occur with the same greatest frequency, each value is used as the mode

Answer 20

Multimodal

Question 21

When no data value occurs more than once

Answer 21

No mode

Question 22

values that divide the distribution into 100 equal parts. P10 or tenth percentile locates the point that is greater than 10 percent of the items in the distribution

Answer 22

Percentiles

Question 23

values that divide a distribution into 10 equal parts. The 1st decile is the 10th percentile; the 2nd decile is the 20th percentile…

Answer 23

Deciles

Question 24

Divide an array into four equal parts, each part having 25% of the distribution of the data values. The 1st quartile is the 25th percentile; the 2nd quartile is the 50th percentile, also the median and the 3rd quartile is the 75th percentile.

Answer 24

Quartiles

Question 25

o single value that is used to describe the spread of the distribution o A measure of central tendency alone does not uniquely describe a distribution

Answer 25

Measures of Dispersion

Question 26

2 TYPES OF MEASURES OF DISPERSION

Answer 26

ABSOLUTE MEASURES OF DISPERSION RELATIVE MEASURE OF DISPERSION

Question 27

difference between the maximum and minimum value in a data set

Answer 27

Range

Question 28

- distance or range between the 25th percentile and the 75th percentile

Answer 28

Interquartile range

Question 29

it measure dispersion to the scatter of the values about there mean

Answer 29

Variance

Question 30

is the square root of variance ● ±1SD = 68.3% ● ±2 SD = 95.4% ● ±3SD = 99.7%

Answer 30

Standard Deviation

Question 31

is a measure use to compare the dispersion in two sets of data which is independent of the unit of the measurement

Answer 31

Coefficient of Variation

Question 32

A distribution is said to be symmetric about the mean, if the distribution to the left of mean is the “mirror image” of the distribution to the right of the mean

Answer 32

symmetry

Question 33

measure of symmetry, or more precisely, the lack of symmetry. A distribution, or data set, is symmetric if it looks the same to the left and right of the center point ● Positively Skew ● Negatively Skew ● Symmetrical Distribution/Equal

Answer 33

Skewness

Question 34

measure of whether the data are peaked or flat relative to a normal distribution. ● Leptokurtic ● Mesokurtic (Normal) ● Platykurtic

Answer 34

Kurtosis

Question 35

a branch of mathematics which deals with the study of possible outcomes of an event or set of events together with the outcomes' relative likelihood and distributions

Answer 35

Probability

Question 36

2 TYPES OF PROBABILITY

Answer 36

OBJECTIVE PROBABILITY SUBJECTIVE PROBABILITY

Question 37

calculated by the process of abstract reasoning

Answer 37

Classical probability

Question 38

depends on the repeatability of some process and the ability to count

Answer 38

relative frequency probability

Question 39

based upon an educated guess

Answer 39

Subjective probability

Question 40

3 PROPERTIES OF PROBABILITY THEORY

Answer 40

1. Given some process ( or experiment) with n mutually exclusive outcomes ( called events), E1, E2, . . . , En, the probability of any event Ei is assigned a nonnegative numbers. That is, P(Ei) ≥ 0 2. The sum of the probabilities of the mutually exclusive outcomes is equal to 1. P(E1) + P(E2) + ... + P(En) = 1 ✔ This is the property of EXHAUSTIVENESS 3. Consider any two mutually exclusive events, Ei and Ej. The probability of the occurence of either Ei or Ej is equal to the sum of their individual probabilities. P(Ei + Ej) = P(Ei) + P(Ej)

Question 41

Calculating the probability of an event

Answer 41

1. Conditional Probability ✔ The condtional probability of A given B, denoted P(A\B), is the probability that event A has occurred in a trial of a random experiment for which it is known that event B has occurred. 2. Joint Probability ✔ Calculates the likelihood of two events occurring together and at the same point in time 3. The Multiplication Rule 4. The Addition Rule 5. Independent Events ✔ When P(A\B) = P(A) * P(B) holds, which in turn is true if and only if P(B\A) = P(B) 6. Complementary Events 7. Marginal Events