PSYC 2111 Test 1

Variance Advantages:

-can be used in equations -every point in distribution contributes to it

Mode Disadvantages

-doesn't represent data well -easily affected w/ 1 or 2 scores

Median Disadvantages

-doesn't represent data well -value may not exists as real score -cannot use with nominal data

Mean Advantages

-every point of distribution contributes to it -can be used in equation -sample mean is an unbiased estimate of population mean

Mean Disadvantages

-influenced by extreme scores -can only be used with I/R data -value may not exist in data

Standard Deviation Disadvantages:

-influenced by extreme scores -need normal distribution and I/R data -biased unless you use n-1 formula.

Range Disadvantages:

-influenced y extreme scores -depends on only 2 points -sometimes impossibe to define

Disadvantages to Within Subjects

-lose subjects over time -order effects (fatigue, practice effects...)

Variance Disadvantages:

-not in same units -influenced by extreme scores -need normal distribution and I/R data -biased unless you use n-1 formula

SD most commonly used because

-same unit as mean -can be used in graphs

Range Advantages:

-simple -used with ordinal and I/R data

Measures of variability indicate...

-spread of distribution -degree to which individual scores are clustered about the mean

Advantages to Within Subjects

-treatment group is control group -fewer subjects needed -can test sequences of development

Mode Advantages

-unaffected by extreme scores -actual score in distribution -can use with any level of measurement

Median Advantages

-unaffected by extreme scores -can use with I/R and Ordinal Data -stable -BEST USED WITH SKEWED DATA

Proportion in tail...

positive= to the right negative =to the left

True Experiment

randomly assign ppl to groups can infer causality

Researchers measure data in a ________ to learn more about individuals in the larger _______ of interest. sample; population statistic; inference population; sample inference; statistic

sample; population

Which of the following distributions has the largest variability? scores: 1, 2, 3, 4, and 5 scores: 22, 24, 26, 28, and 30 scores: 2, 3, 4, 5, and 6 scores: 1, 3, 6, 9, and 12

scores: 1, 3, 6, 9, and 12

If you have 61 scores, which score is the median? the 31st score the 32nd score it is impossible to tell without the dataset the 33rd score

the 31st score

Between Subjects

participant only exposed to one level of IV

Percentile Rank

particular persons rank relative to reference group (what % scored lower OR TO THE LEFT)

The use of tables and graphs to summarize data is an example of

Descriptive statistics

Statistical analysis allows researchers to...

Evaluate scientific observations

An interquartile range removes...

the top and bottom 25% of scores in a distribution before calculating range

To minimize subject attrition

Start with more people then you need

What is an operational definition for aggression?

How many times a person kicks another person

True and Quasi

Categorical IV and continuous DV

To minimize fatigue/practice effects

Counterbalance levels of IV

Histogram

I/R on X axis Frequency on Y axis bar touchs b/c CONTINOUS variable

Sum or deviations from mean always....

= 0

Bar Graph

bars do not touch b/c distinct categories NOT CONTINUOUS

Standard Deviation Advantages:

-same units as scores -can be used in equations -every point in distribution contributes to it

The standard normal distribution is normally distributed with a mean of ____ and a variance of ____. 1; 0 any positive value; any value any value; any positive value 0; 1

0; 1

Which type of graph has bars that touch?

A histogram

Why do use probability models

B/c we can't access whole population

Normal Distribution

Bell shaped unimodal symmetrical asymptotic

Correlation

Continuous IV and DV

Or will be ...... than and in probability

Higher

A researcher tests whether the dosage level of some drug (low and high) causes significant differences in health. To do this the researcher randomly assigns rat subjects to receive a low or high dosage of the drug and records health-related measures in both groups. What type of design is this?

Experiment and between-subjects

A researcher records the following data: 4, 4, 4, 4, and 3. How would you describe the variability of these data? It is equal to zero because scores are approximately the same. It is very large (much greater than 10) because 3 is an outlier in the data. It is negative because 3 is less than the other scores in the distribution. It is very small (close to 0) because scores are approximately the same.

It is very small (close to 0) because scores are approximately the same.

Nominal Scale

Mutually exclusive categories (political affiliation, position on team...) -used with Mode

Ordinal Scale

Mutually exclusive categories, and logical order, RANK is key word. (rank in army, list of preferred veggies) -used with Mode and Median

I/R Scale

Mutually exclusive categories, logical order, equal distance between values, and true zero point (age, height, weight) -used with mode, median, mean

Which term is least likely to describe qualitative data?

Numeric

Which of the following is NOT a characteristic of probability? Probability can never be negative. Probability is most useful for describing fixed events. Probability can be stated as a fraction or decimal. Probability varies between 0 and 1

Probability is most useful for describing fixed events.

Which one of the following is the bigger area for any z-score that is not exactly 0?

The body

How do we use probability in statistics? We use probability models to make decisions about whether two groups are statistically different We use probability models to figure out what percent of a sample is lying on some test We use probability models to choose the best operational definitions for our variables all of the above

We use probability models to make decisions about whether two groups are statistically different

What is the difference between a grouped and ungrouped frequency distribution?

a grouped frequency distribution has X values that are intervals, while an ungrouped frequency distribution has X values that are single values

Quasi Experiment

cannot randomly assign ppl to groups

Why is a z score useful?

convert any score to a z-score to find percent, ect.

The use of tables and graphs to summarize data is an example of inferential statistics interpretation descriptive statistics generalization

descriptive statistics

Within Subjects

each participant is exposed to all levels of IV

What's a z score?

how many SD'S you are from the mean score on normal distribution (mean=0, SD= 100)

Only positive z-scores on table b/c...

it's symmetrical

What is the best measure of central tendency if you have a skewed distribution? mode median mean it is impossible to know without seeing the graph

median

Which measure(s) of central tendency is unaffected by extreme scores? mode only mode and median median only mode, median, and mean

mode and median

In probability, and means...

must meet both criteria

An animal researcher measures the number of times a rat presses a lever located at the right, center, and left of a cage for a food reward. What scale of measurement is the location of lever pressing? nominal ordinal interval/ratio not enough information to determine

nominal

Degrees of freedom

number of values in a data set can vary, given a statistic of data n-1

Which of the following terms are least likely to be used to describe qualitative data? nominal descriptive categorical numeric

numeric

Percentile

values that divide the distribution into 100 equal parts

Mean=Median=Mode

when all # are the same normally distributed

You are instructed to subtract 4 points from each score and find the sum of the resulting values. How would this set of instructions be expressed in summation notation? ΣX - 4 4 - ΣX Σ (X - 4) Σ(4 - X)

Σ (X - 4)