Midterm 1 Material

Question 1

What is the mean?

Answer 1

• Mean or average
• We calculate the average by adding all the numbers together and dividing it by the number of values.
• It can be represented as ȳ = mean of a sample

Question 2

What does “n” signify?

Answer 2

n signifies sample size

Question 3

What does yi rep?

Answer 3

yi represents one observation in the sample

Question 4

What is the median?

Answer 4

Median is the midpoint of the ordered sample

• Median = (N + 1) / 2

Question 5

What is mode?

Answer 5

Value that occurs most frequently in the distribution.

Question 6

What is distribution?

Answer 6

Distribution is just a way of organizing and showing data. Think of it as a list or picture that shows where all the data points are and how often they appear.
- It’s like grouping similar data points together to see patterns.

• Unimodal (having one mode)

-Bimodal (having 2 modes)

-Multimodal (having 3 modes)

Question 7

What is a deviation?

Answer 7

• Difference between an observation and the mean (i.e. how far an observation ‘falls’ from the mean of the population or the sample)

To calculate deviation;
(yi)= yi - ȳ

Question 8

What is a standard deviation

Answer 8

Typical (average) deviation from the
mean for an observation in the set
(population or sample).
- σ means population standard
deviation (‘sigma’)

To calculate population standard deviation:

σ = √[Σ(yi – μ)2 / (N – 1)]

Question 9

What is the Empirical Rule

Answer 9

If the distribution is normal (symmetrical) bell-shaped

• 68% of observations fall between the mean and one standard deviation on either side.
• 95% of observations fall between the mean and two standard deviations on either side.
• Over 99% of observations fall between the mean and three standard deviations on either side.

Question 10

What is Quartile

Answer 10

Measure of data dispersion breaking down the distribution in four ordered segments.

• When ordered in ascendance, the first 25% of the data distribution comprise the lower quartile, whereas the first 75% of the distribution comprise the upper quartile. Quartiles are typically ordered as
  follows:
• Min: 0% of the data
• Q1: First 25% of the data
• Med: First 50% of the data
• Q3: First 75% of the data
• Max: Fully 100% of the data

Question 11

Data

Answer 11

Factual information about things that
we observe

Question 12

Population

Answer 12

Total set of subjects of interest in a
study

Question 13

Sample

Answer 13

Subset of the population on which the
study collects data

Question 14

Parameter

Answer 14

Numerical summary of the population

Question 15

Statistic

Answer 15

Numerical summary of the sample data

Question 16

Descriptive statistics:

Answer 16

Statistics summarizing (outlining)
sample or population data

Question 17

Inferential statistics:

Answer 17

Statistics making predictions about population parameters based on sample
data

Question 18

Variable

Answer 18

Characteristic that can vary in value
among subjects in a sample or a population.

Question 19

Discrete variable:

Answer 19

Variable taking the form of a set of
separate numbers, such as 0, 1, 2, 3.

Question 20

Continuous variable

Answer 20

Variable that can take an infinite continuum of real number values

Question 21

Random sampling

Answer 21

Drawing a sample of n subjects who each
have the same probability of being drawn

Question 22

What are the three main ways data can be biased; sampling error?

Answer 22

Sample bias
*Response bias (e.g. under /over-reporting)
*Non-response bias

Question 23

Sampling bias

Answer 23

occurs from using nonprobability samples, such as the selection
bias inherent in volunteer samples.

Question 24

Response bias

Answer 24

occurs when the subject gives an incorrect response (perhaps
lying), or the question wording or the way the interviewer asks the questions is
confusing or misleading

Question 25

Nonresponse bias

Answer 25

occurs when some sampled subjects cannot be reached or refuse to participate or fail to answer some questions.

Question 26

What is the z score?

Answer 26

It refers to the number of of standard deviations that an observation can fall from the mean.

Question 27

What is Population mean?

Answer 27

the average of the observations for the entire population.

Question 28

What is the population standard of deviation?

Answer 28

The population standard deviation describes the variability of those observations about the population mean

Question 29

sampling distribution

Answer 29

enables us to predict how close a sample mean falls to the population mean

Question 30

Probability

Answer 30

that outcome is the proportion of times that the outcome would occur in a very long sequence of observations.

Question 31

The higher the confidence interval

Answer 31

the larger our confidence interval (margin of error) will be

Question 32

The lower our confidence level

Answer 32

the smaller our confidence interval (margin of error) will be (i.e. the more precise our estimation will be).