W1 Chapter 3A - Essentials Statistical Concepts

Question 1

How can large amounts of data collected in tests be used in a meaningful manner?

Answer 1

By summarising data using statistical tools like measures of central tendency

Question 2

One way of summarising data is to tabulate a frequency distribution. What is frequency distribution?

Answer 2

A tally of how many scores of a specific equal-sized class interval fall into each interval

Question 3

What range of class intervals is common for frequency distributions?

Answer 3

Between 5 - 15 class intervals

Question 4

What other type of graphical representation contains the same information as frequency distributions?

Answer 4

Histograms

Question 5

What component of a histogram represents the number of scores within that class interval?

Answer 5

The height of the column

Question 6

How does a frequency polygon differ from a histogram?

Answer 6

The frequency of class intervals is represented by a single point rather than a column, and the points are connected with a line

Question 7

What are the 3 type of measure of central tendency?

Answer 7

1. Mean (average)
2. Median (Middle)
3. Mode (most frequent)

Question 8

What can make the mean unreliable?

Answer 8

A few extreme high or low scores

Question 9

When is the median a better measure of central tendency?

Answer 9

When the distribution of score is skewed, or asymmetrical.

Question 10

What is the most commonly used statistical index of variability in a group of scores?

Answer 10

Standard deviation

Question 11

What does the standard deviation represent?

Answer 11

The degree of dispersion in a group of scores

Question 12

What 2 statistical indices is used to describe the degree of dispersion in a distribution?

Answer 12

1. Variance
2. Standard Deviation

Question 13

What is the relationship between variance and standard deviation?

Answer 13

The standard deviation the the square root of the variance

Question 14

What is the preferred measure of variance?

Answer 14

Standard deviation

Question 15

How is a normal distribution defined?

Answer 15

By a symmetrical, mathematically defined bell curve

Question 16

What are the 3 reasons why a normal distribution is preferred?

Answer 16

1. A normal distribution has useful mathematical features that form the basis for several kinds of statistical investigations (such as the t-test)
2. Mathematical precision
3. A normal curve often arises spontaneously in nature

Question 17

What is the percentage of cases within one standard deviation?

Answer 17

68.26%

Question 18

What is the percentage of cases within two standard deviations?

Answer 18

95.44%

Question 19

What is the percentage of cases within three standard deviations?

Answer 19

99.72%

Question 20

What does skewness refer to?

Answer 20

The symmetry or asymmetry of a frequency distribution

Question 21

What is positive skewness?

Answer 21

When the test scores are piled up at the low end of the scale

Question 22

What is negative skewness?

Answer 22

When the test scores are piled up at the high end of the scale

Question 23

What can be done when an instrument produces sewed results?

Answer 23

A statistical transformation can be used to produce a more normal distribution