Stats Exam 1

A Branch of mathematics that is used to describe, organize, and interpret a group of numbers or observations.

What are the goals of statistics?

Goal is to summarize numbers and make sense of what we observe

What is the difference between "descriptive" statistics and "inferential" statistics?

Descriptive: Used to organize and describe a collection of data (Some cat weight)Inferential: used to make inferences beyond the data you actually have. (All cat weight)

Sample

A subset of the cases of interest

Population

The entire set of cases of interest.

Sample statistic

A number that quantifies a characteristic of a sample

Population parameter

a number that quantifies the characteristic of a population.

How is the size of your sample related to your ability to accurately estimate the population parameter(s) that you are interested in?

As you increase the size of your sample, your stats become more accurate

Why is it important for a researcher's sample to be "representative" of the population that he or she is interested in?

Because it will be more accurate.

To maximize their chances of obtaining representative samples, researchers often employ a technique called ___________ _________. The defining property of this technique is that each member of the population has a(n) ________ chance of being included in the sample.

Random Sampling, Equal

Variable

Any characteristic that can take on different values

Constant

Any Characteristic that does not vary.

What is the difference between an "independent variable" and a "dependent variable"?

a. Independent: Manipulated by the experimenterDependent: Measured by the experimenter

Which one (Independent/dependent) do researchers manipulate when they conduct experiments?

Independent

Which one (Independent/dependent) do researchers measure when they conduct experiments?

Dependent

Which one (Independent/dependent) represents the hypothesized "cause"?

Which one (Independent/dependent) represents the hypothesized "effect"?

What is "random assignment"? Why is it so important in experiments?

Every participant has an equal chance of being assigned to the "experimental or control group.

What is the difference between a "discrete" variable and a "continuous" variable?

a. Discrete: Can only take specific valuesb. Continuous: can take on any value between any two specifies values.

If a variable can differ in "kind" or "quality"—but not in "amount" or "magnitude"— then we would say that this variable can only be measured on the ________ scale.

Nominal

Suppose that "A," "B," and "C" are three different values that a particular variable can have. You know that A is greater than B, and you know that B is greater than C, but you aren't sure whether the difference between A and B is the same as the difference between B and C. This variable is most characteristic of which scale of measurement?

ordinal scale

On the "interval" scale of measurement, what do you know about the differences (or "gaps") between adjacent values?

The gaps are equal

There is no "true zero point" (or "absolute zero") on the interval scale of measurement—what does this mean?

Means that the score of zero does not indicate the total absence of the variable being measured

Why is the "ratio" scale considered the highest scale of measurement

Because it has the most precise level of measurement.

What can you do with "ratio" values that you cannot do with values on the other scales of measurement?

Allows computation of ratios. (twice as fast; half as many.)

Why are "averages" also referred to as "measures of central tendency"?

They are single values that tend to be located near the center of a distribution.

The ______ is the most common measure of central tendency.

Mean

What is the "mean"? How do we calculate it?

The mean is the sum of all scores divided by the total; number of scores.

Why did I describe the mean as the "balancing point" for the distribution?

Because the total distance of all above mean scores is equal too the total distance of all below mean scores

What are "outliers," and how do they affect the mean?

Outliers are extreme scores2.1 The number is usually reallllly different from the rest of the values, and the mean is dependent on all it's values, so the outliers will mess things up.

What is the "median"?

The middlemost score - divides distribution in half

The first step in determining the median involves listing the scores in order.

From greatest to least

What formula do we use for determining the position of the median?

(mdm)= (n+1)/2

If n is an even number, then this formula will produce a position that ends in ".5" —how do we calculate the median when this occurs?

Find the two middlemost numbers, add them, then divide the sum by 2.

If we have outliers in our data set, then the median better represents the "center" of the distribution than the mean does—why?

Because the median is less reliant on outliers

What is the "mode"?

The value that occurs most frequently

The mode is the only measure of central tendency that can be used with variables that have been measured on the _____ scale of measurement.

ANY

What is a "bimodal" distribution?

When you have two modes

Define the term "variability.

How much individual scores tend to differ from one another

What is the "exclusive range"? How do we calculate it?

a. Simplest measure of variabilityb. Range= h-l

Why does the range only give us a very rough measure of variability?

Because it is very sensitive to outliers

a. How do outliers affect the range?

Very sensitive to outliers.

What is the "inclusive range," and how do we calculate it?

Used to describe the variability of a continuous variable.ii. Inclusive= h - L + 1

What is the "interquartile range" (IQR)?

Identifies the range of the middle 50% of the distribution

Compared to the range, the IQR is relatively insensitive to extreme scores—why?

IQR is not effected by extreme scores, because it only deals with the middle 50% of the distribution

How do we calculate the IQR?

IQR= Q3 - Q1

What are "quartiles"?

Scores that divide distribution into quarters

Slashing