Week 1: The Descriptive Stats of Outcomes - How is the Data Distributed and How can we Assess the Distribution

Question 1

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What distribution is needed for parametric tests?

Answer 1

A normal distribution

Question 2

The normal distribution curve is also referred as the

Answer 2

bell curve

Question 3

Normal distribution is symmetrical meaning

Answer 3

This means that the distribution curve can be divided in the middle to produce two equal halves

Question 4

The bell curve can be described using two parameters called (2)

Answer 4

1. Mean (central tendency)
2. Standard deviation (dispersion)

Question 5

μ is

Answer 5

mean

Question 6

σ is

Answer 6

standard deviation

Question 7

Diagram shows:

Answer 7

e.g., If we move 1σ to the right then it contains 34.1% of the valeues

Question 8

Many statistical tests (parametric) cannot be used if the data are not

Answer 8

normally distributed

Question 9

The mean is the sum of

Answer 9

scores divided by the number of scores

Question 10

Mean is a good measure of

Answer 10

central tendency for roughly symmetric distributions

Question 11

The mean can be a misleading measure of central tendency in skewed distributions as

Answer 11

it can be greatly influenced by scores in tail e.g., extreme values

Question 12

Aside from the mean, what are the 2 other measured of central tendency? - (2)

Answer 12

1. Median
2. Mode

Question 13

The median is where (2)

Answer 13

the middle score when scores are ordered.

the middle of a distribution: half the scores are above the median and half are below the median.

Question 14

The median is relatively unaffected by … and can be used with… (2)

Answer 14

• extreme scores or skewed distribution
• can be used with ordinal, interval and ratio data.

Question 15

The mode is the most

Answer 15

frequently occurring score in a distribution, a score that actually occurred

Question 16

The mode is the only measure of central tendency that can be used with

Answer 16

with nominal data

Question 17

The mode is greatly subject to

Answer 17

sample fluctuations and is therefore not recommended to be used as the only measure of central tendency

Question 18

Many distributions have more than one

Answer 18

mode

Question 19

The mean, median and mode are identical in

Answer 19

symmetric distribtions

Question 20

For positive skewed distribution, the

Answer 20

mean is greater than the median, which is greater than the mode

Question 21

For negative skewed distribution

Answer 21

usually the mode is greater than the median, which is greater than the mean

Question 22

Kurtosis in greek means

Answer 22

bulge or bend in greek

Question 23

What is central tendency?

Answer 23

the tendency for the values of a random variable to cluster round its mean, mode, or median.

Question 24

Diagram of normal kurotsis, positive excess kurotsis (leptokurtic) and negative excess kurotsis (platykurtic)

Answer 24

Question 25

What does lepto mean?

Answer 25

prefix meaning thin

Question 26

What is platy

Answer 26

a prefix meaning flat or wide (think Plateau)

Question 27

Tests of normality (2)

Answer 27

Kolmogorov-Smirnov test Shapiro-Wilks test

Question 28

Tests of normality is dependent on

Answer 28

sample size

Question 29

If you got a massive sample size then you will find these normality tests often come out as .... even when your data visually can look - (2)

Answer 29

significant normally disttibuted

Question 30

If you got a small sample size, then the normality tests may look non-siginificant, even when data is normally distributed, due to

Answer 30

lack of power in the test to detect a significant effect

Question 31

There is no hard or fast rule for

Answer 31

determining whether data is normally distributed or not

Question 32

Plot your data because this helps inform on what decisions you want to make with respect to

Answer 32

normality

Question 33

Even if normality test is sig and data looks visually normally distributed then still do

Answer 33

parametric tests

Question 34

A frequency distribution or a histogram is a plot of how many times

Answer 34

each score occurs

Question 35

2 main ways a distribution can deviate from the normal - (2)

Answer 35

1. Lack of symmetry (called skew) 2. Pointyness (called kurotsis)

Question 36

In a normal distribution the values of skew and kurtosis are 0 meaning...

Answer 36

tails of the distribution are as they should be