STATS EXAM 1

Skewness

A measure of the shape of a data distribution. Data skewed to the left result in negative skewness; a symmetric data distribution results in zero skewness; and data skewed to the right result in positive skewness.

population sampling

The process through which a group of representative individuals is selected from a population for the purpose of predicting the entire population.

Z Score Example

You have a test score of 190 The test has a mean (average) of 150 And a standard deviation of 25 z=(x-u)/ó . z=(190-150)/25= 1.6

normal distribution

a bell-shaped curve, describing the spread of a characteristic throughout a population

statistical significance

a statistical statement of how likely it is that an obtained result occurred by chance

Descriptive statistics have which of the following properties? a. they are numerical or graphical summaries of data b. they are used to examine relationships between variables in a data set c. they are used to see how well sample data can be generalized to the population d. all of the above

a. they are numerical of graphical summaries of data

mean

average

Skewness refers to the a. shape of the top of the curve b. extent to which data are not symmetrical about the center c. presence of outliers d. sample

b. extent to which data are not symmetrical about the center

Standard deviation is best described by which of the following statements? a. it can be used to compare variation between two or more variations b. it is the average distance of each point from the mean c. it is the variance squared d. both a and b are correct

b. it is the average distance of each point from the mean

The 50th percentile is always the a. mean b. median c. standard deviation d. a and b

b. median

The null hypothesis states a. the expected fire oof the relationship between the variables b. that no relationship will be found c. that a relationship will be found but it will not state the direction d. none of the above

b. that no relationship will be found

If a statistical test is significant it mean that a. it has important clinical applications b. the study had acceptable power c. the null hypothesis was rejected d. all of the above are true

c. the null hypothesis was rejected

A z-score can give information about a. the standard deviation of a distribution b. the mean of a distribution c. the percentile rank of a data point d. none of the above

c. the percentile tank of a data point

The a-level is defined by a. the probability of making a type 1 error b. the probability of making a type 2 error c. the researchers at the start of a study d. a and c only

c. the researcher a the start of a study

A sample population curve is more likely to look like the population curve when a. the bell shape is wide b. the sample size is small c. the sample size is greater than 30 d. none of the above

c. the sample size is greater than 30

Class intervals should be a. overlapping intervals b. of equal lengths c. mutually exclusive d. b and c only

d.

Symmetrical distributions are best described by which of the following statements? a. They are normally distributed b. They have a U-shaped distribution c. They have small standard deviations d. They have an equal number of data points that appear to the left and to the right of the center

d. They have an equal number of data points that appear to the left and to the right of the center

A normal distribution is characterized by a. a bells shape b. a mean, median, and mode that are equal c. a total area under the curve above the x-axis that is 1 d. all of the above

d. all of the above

Power can be increased by a. increasing the a-level b. increasing the sample size c. increasing the effect size d. all of the above

d. all of the above

Power is defined by a. the a-level b. the sample size c. the effect size d. all of the above

d. all of the above

What is standard deviation?

is mean (average) distance of each point from the mean

I error within Stats

is the rejection of a true null hypothesis ('false positive")

p(a) within stats

marginal probability of event A

What is a z-score?

number of standard deviations from the mean z=(x-u)/ó

Class intervals

should have no overlapping , exhaust all values in the data, and

null hypothesis

the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.

Median

the middle score in a distribution; half the scores are above it and half are below it

Mode

the most frequently occurring score(s) in a distribution