Statistics

Question 1

Median- The point/score at which 50% of scores fall below it and 50% fall above it

Answer 1

Median

Question 2

This is the most general and least precise measure of central tendency

When two values occur the same number of times – Bimodal distribution

Answer 2

Mode - most frequently occurring value

Question 3

Mode is more frequent than median and mean

Answer 3

negatively skewed

Question 4

Mean, median, mode similar frequency

Answer 4

normal

Question 5

Mode and median are more frequent than mean

Answer 5

positively skewed

Question 6

quantifies the amount of variability, or spread, around the mean of the measurements.
To calculate: take each difference from the mean, square it, and then average the result

Answer 6

Variance (σ2)

To calculate: take each difference from the mean, square it, and then average the result

Question 7

measure of variation of scores about the mean

Answer 7

Standard deviation (σ)

Question 8

To calculate: take the √ of the variance
(the “average distance” to the mean)
In practice, the standard deviation is used more frequently than the variance.
Primarily because the standard deviation has the same units as the measurements of the mean.
When comparing two groups, the group with the larger standard deviation exhibits a greater amount of variability (heterogeneous) while the groups with smaller deviation has less variability (homogeneous

Answer 8

Standard deviation (σ)

Question 9

A useful summary of a set of bivariate data (two continuous variables)
Gives a good visual picture of the relationship between the two variables, and aids the interpretation of the correlation coefficient or regression model.

Answer 9

Scatterplots

Question 10

The absolute value of the coefficient (its size, not its sign) tells you how strong the relationship is between the variables.
Tells us how strongly two variables are related

Answer 10

Correlation Coefficient

Question 11

“r” can not be > 1 or < -1
Closer to -1 or +1: the stronger the relationship
Closer to 0 : the weaker the relationship

Answer 11

Correlation Coefficient

Question 12

The most common measure of association. Results can misleading if the relationship is non-linear

Answer 12

Pearson’s correlation is very sensitive to outlying values.

Question 13

The statement of no difference or no relationship between the variables

Answer 13

Null hypothesis (Ho)

Question 14

The statement that establishes a relationship between variables being assessed

Answer 14

Alternative hypothesis (Ha or H1)

Example: In a clinical trial the hypothesis states the new drug is better the placebo

Question 15

error is made if we reject the null hypothesis when null hypothesis is true

Answer 15

type I

Question 16

known as an acceptance error or an β error

if we fail to reject null hypothesis

Answer 16

Type II error

Question 17

The probability of finding an effect

The probability of correctly rejecting the null hypothesis

The probability of seeing a true effect if one exists

Designers of studies typically aim for a power of 80% or 0.8

Implies there is an 80% chance of getting it right

Generally speaking: More people = more power

Answer 17

Statistical power

Question 18

calculates the number of participants a study must have to draw accurate conclusions

Answer 18

power analysis

Takes into consideration: estimated effect size, sample means, etc

Question 19

The probability of rejecting a true H0

α = .05 usually set, acceptable error

Answer 19

Statistical significance and p-value

Question 20

Accepted value is 5% risk (p = .05)

Means there is a 5% chance that the results happened by chance

Answer 20

Allows us to reject or accept the null hypothesis

Question 21

chance of random error

Answer 21

p

Question 22

the acceptable error

Answer 22

α

Question 23

p ≤ α

Answer 23

reject the H0

the results are statistically significant

Question 24

p > α

Answer 24

fail reject the H0

the results not statistically significant