cogs 14b definitions

Question 1

What is statistics?

Answer 1

quantification and interpretation of variability

Question 2

Discrete Variables

Answer 2

a variable that takes on distinct, countable values ; giving whole numbers

examples: # of siblings, political party

Question 3

Continuous Variables

Answer 3

have potentially infinite values between any two observed values

examples: height, weight, interest rates

Question 4

What are the three levels of measurement?

Answer 4

Nominal, Ordinal (ranked), Interval/Ratio

Question 5

Define Nominal data fa me?

Answer 5

variables that have two or more categories, but which do not have an intrinsic order

examples: sex, blood type, favorite kpop group

Question 6

Define Ordinal (ranked) data fa me?

Answer 6

a set of categories that are organized in and ordered or ranked sequence ; possesses an inherent order

examples: letter class grades, clothing size

Question 7

Define Interval/Ratio data fa me?

Answer 7

• used to measure variables with equal intervals between values
  ~ interval has no true zero point while ratio does
  ~ quantitative

interval example: IQ score, GPA
ratio example: distance, weight, income

Question 8

Population

Answer 8

Complete collection of observations or potential observations
for all individuals or units of interest

Question 9

Sample

Answer 9

A partial set of observations taken from the population

Question 10

Convenience sample

Answer 10

respondents from a population that can be conveniently
contacted/accessed by the researcher

examples: from a poll, survey, people in crowded locations

Question 11

Parameter

Answer 11

value reflecting something in the entire population of interest

Question 12

Statistic

Answer 12

a value that reflects something from a sample (can be estimate
of population parameter)

Question 13

Random sampling

Answer 13

all potential observations in the population have an
equal chance of being selected in a sample

Question 14

Sampling error

Answer 14

samples can be unrepresentative of the whole population to varying degrees and this causes errors of varying sizes based on level of representativeness - due to this, sample statistics will
vary by chance

Question 15

Descriptive Statistics

Answer 15

Provides description of data collected
- Approaches presentation of data in a digestible manner
- How can we organize the sample data?
- Measures of central tendency and variability, mean, median, mode

Question 16

Inferential Statistics

Answer 16

Helps figure out how sample of data will generalize
- Makes inferences and estimates using data
- Hypothesis testing, confidence intervals, regression analysis, ANOVA
- What does the sample data say about the population?

Question 17

Bar Charts
when is best used?

Answer 17

• Best used when x-axis var is discrete and nominal
• Used for presentation of summary stats or raw data
• Differences easy to see

Question 18

Line charts
what is best used for and useful for indicating?

Answer 18

• X-axis variable is continuous and interval/ratio (quantitative data)
• Useful for indicating trends over time

Question 19

Scatter Plots
best used for what kinda data and what kind of values?

Answer 19

• Best used when both x and y coordinate values are interval/ratio scale
• best used for bivariate data ; used in observational studies with no independent variables
• X & Y coordinates represent values of 2 diff variables

Question 20

Frequency distributions

Answer 20

sorting observations into classes and displaying the number of occurrences in those classes
(can be shown using a histogram or table)

Question 21

Ungrouped frequency
distribution

Answer 21

• distribution that displays the frequency of each individual data value instead of groups of data values
• best to use when you have less
  than 20 single-value classes

Question 22

Grouped Frequency Distribution
only possible with what data? and what does it organize?

Answer 22

• organizing a large set of data into classes with more than 1 value
• only possible with ordinal and interval/ratio data
• even if a group has 0 observations, it is included
• choose appropriate bins based on # of observations

Question 23

Outliers

Answer 23

extreme scores or observations - they lie at the far edge of the frequency distribution and are extremely unlike rest of the sample

Question 24

Relative frequency (f) distributions

what does it display? and it’s helpful when…?

Answer 24

• display the frequency of each class as a proportion
• helpful when discussing ratios
• distribution that shows the proportion of the total number of observations associated with each value or class of values

Question 25

Cummulative frequency
distributions

Answer 25

frequency distribution that represents the sum of a class and all classes below it

Question 26

Relative cumulative distributions

Answer 26

Divide cumulative freq. by # of observations

Question 27

Positively skewed

Answer 27

• extreme values lie to the right of the distribution
• goes up then down

Question 28

Negative skewed

Answer 28

• extreme values lie to the left of the distribution
• goes up so starts low then rises

Question 29

Mean and what its best for

Answer 29

• the average value of a data set
• appropriate for interval/ratio data
• affected by outliers

Question 30

Population mean (𝜇)

Answer 30

a parameter - the mean of the whole population

Question 31

Sample mean (x̄)

Answer 31

a statistic - the mean of a sample of the population /
estimate of the population mean

Question 32

Define Median

how do you get it? what is it best used for? is it impacted by outliers?

Answer 32

• middle value when data is organized from smallest to largest value
• best for ordinal, interval, or ratio data
• not impacted by outliers

Question 33

How do you calculate median?

Answer 33

Steps to calculate median:

1) Order observations in ascending order

2) Find middle position by adding 1 to total number of observations &
dividing by 2

3) If you have an odd number of data points, the middle value will be the median, but if if it is even, add the number above the middle position and divide by 2

Question 34

Mode and what it works for

Answer 34

• value or category that has the greatest frequency
• only measure of central tendency that can be used for nominal data (works for all 4 data types - ordinal, interval, ratio, nominal)
• not impacted by outliers

Question 35

Variability

Answer 35

the degree to which scores in a distribution are spread out or clustered together

Question 36

Interquartile Range (IQR)

Answer 36

the range covered by the middle 50% of the
data - this measure is much more resistant to extreme/outlier values
because it does not count in the lower and upper extreme values

Question 37

How do you calculate (IQR)?

Answer 37

1) Arrange data from lowest to highest

2) Find quartile index ((n+1)/4) and round to the nearest whole # if needed

3) With index number, count to max to get 3rd quartile

4) Count to min with index number to get 1st quartile

5) IQR: 3rd quartile - 1st quartile

Question 38

Standard Deviation

what does it measure? and how does it measure whats being measured lol?

Answer 38

measures variability by measuring how the scores differ from the mean

Question 39

What is Variance and how do you calculate it?

Answer 39

• variance is the mean of all deviation scores
• the equation is SS/N

Question 40

Sum of Squares (SS)

Answer 40

the sum of all values in a data set with the mean
subtracted from it and then squared