psych 10 exam 2 study guide

How would you find what percentile a given raw score is? Remember, you have to turn the raw score into a z score because , "we don't know about raw scores, so we have to turn the raw scores into z scores"..... then, look in the z table.... Also, don't forget to draw your distributions to visually show yourself the areas of the distribution that are of concern or interest

- turn the raw score into a z- score -if the Z core is positive look at column a then move finger to column b and turn that value to a percentage. then add 50% - if z- score is negative then look at column a then move finger to column c and turn that value into a percentage.

What does "homogeneity of variance" mean?

A characteristic of data describing populations represented by samples in a study that have the same variance

What does "Relative Standing" mean?

A description of a particular score derived from a systematic evaluation of the score using the characteristics of the sample or population in which it occurs

What is the sampling distribution of differences between means?

A frequency distribution showing all possible differences between two means that occur when two independent samples of a particular size are drawn from the population of scores described by the null hypothesis

What is a sampling distribution?

A frequency distribution showing all possible sample means that occur when samples of a particular size are drawn from the raw score population described by the null hypothesis formula 1b

What is "probability," and how does that related to "relative frequency?"

A mathematical statement indicating the likelihood that an event will occur when a particular population is randomly sampled; symbolized by p

What is random sampling?

A method of selecting samples so that all members of the population have the same chance of being selected for a sample

What is the mean and standard deviation of the z distribution?

A normal distribution with a mean of 0 and a standard deviation of 1 is called a standard normal distribution

What is a confidence interval?

A range of values of u, one of which is likely to be represented by the sample mean

What does it mean to have a representative sample?

A sample whose characteristics accurately reflect those of the population

What is the central limit theorem?

A statistical principle that defines the mean, standard deviation, and shape of a theoretical sampling distribution

What is the "standard normal curve?"

A theoretical perfect normal curve, which serves as a model of the perfect normal z-distribution - symmetrical - bell shaped

What is the estimated standard error of the mean based on?

An estimate of the standard deviation of the sampling distribution of means, used in calculating the one-sample t-test; symbolized by Sx

What are inferential statistics?

Procedures for determining whether sample data represent a particular relationship in the population

How would you go about finding a raw score from a given percentile? You have to work backwards...... find the proportion, identify the z score, and then plug this into the relevant formula.

- if percentile is above 50th percentile then subtract 50% then turn that percentage to a decimal.Then go to column b for that value then move your finger to column a. Then take that score and plug it into the formula x = mean + z-score( standard deviation) - if percentile is under 50th percentile then just turn that into a decimal. Then go to column C and move finger to column A.

You should know how to find the proportion or percentage of scores between two raw scores— remember, "we don't know about raw scores, so we have to turn the raw scores into z scores"..... then, look in the z table.

- score - mean / standard deviation for both raw scores - find the Z values for both answers - subtract second z - score to first and then change to a percentage

You should know how to find the proportion or percentage of scores between two z-scores—remember, you'll need the z table for this.

- subtract z - scores then turn it to a percentage

What is the "region of rejection?"

That portion of a sampling distribution containing values considered too unlikely to occur by chance, found in the tail or tails of the distribution

alpha

The Greek letter a , which symbolizes the criterion, the size of the region of rejection of a sampling distribution, and the theoretical probability of making a Type I error

What is the difference between independent and dependent events?

independent event - Events for which the probability of one is not influenced by the occurrence of the other -dependent event - Events for which the probability of one is influenced by the occurrence of the other

Statistical hypotheses: Null and the alternative hypotheses

null - The statistical hypothesis describing the population parameters that the sample data represent if the predicted relationship does not exist; symbolized by Ho alternative - The statistical hypothesis describing the population parameters that the sample data represent if the predicted relationship does exist; symbolized by Ha

What do you have to do to find if a "sample represents a population?" That is, what test would you do???

one sample z-test?

How do critical values change as a result of making one-and two-tailed hypotheses?

two tail - the criterion is split into two therefore having to critical values. if criterion = 0.05 crit values = +- 1.96 - one tail - all the criterion is on one tail so the critical value is smaller meaning the region of rejection in one tail is greater. if criterion = 0.05 crit value = 1.645

Type I and II errors

type 1 - A statistical decision-making error in which a large amount of sampling error causes rejection of the null hypothesis when the null hypothesis is true (that is, when the predicted relationship does not exist) type 2 - A statistical decision-making error in which the closeness of the sample statistic to the population parameter described by the null hypothesis causes the null hypothesis to be retained when it is false (that is, when the predicted relationship does exist)

What is the difference between sampling with and without replacement?

with replacement - A sampling procedure in which previously selected individuals or events are returned to the population before any additional samples are selected without replacement - A sampling procedure in which previously selected individuals or events are not returned to the population before additional samples are selected

What is the difference between the independent and dependent samples t test?

independent - The t-test used with data from two independent samples dependent - The t-test used with data from two related (dependent) samples

What is a deviation score?

how far a score is from the mean (x-M) the difference of a raw score from the mean

What is sampling error?

The difference, due to random chance, between a sample statistic and the population parameter it represents

What is the standard error of the differences?

The estimated standard deviation of the sampling distribution of differences between the means of independent samples in a two sample experiment; symbolized by Sx1 - Sx2

When do you use the one sample t test?

The parametric procedure for a onesample experiment when the standard deviation of the raw score population must be estimated

What is a "probability distribution?"

The probability of every event in a population, derived from the relative frequency of every event in that population

What is "power" and how do you increase it?

The probability that a statistical test will detect a true relationship and allow the rejection of a false null hypothesis - increase power by having a larger N - do a one tailed test

What is meant by the "criterion?

The probability that defines whether a sample is too unlikely to have occurred by chance and thus is unrepresentative of a particular population

Standard error of the mean

The standard deviation of the sampling distribution of means; used in the z -test (symbolized by Ox ) and estimated in the one-sample t -test (symbolized by Sx)

What is a "z-score," and what information does it give in terms of a distribution?

The statistic that describes the location of a raw score in terms of its distance from the mean when measured in standard deviation units; symbolized by ; also known as a standard score because it allows comparison of scores on different kinds of variables by equating, or standardizing, the distributions

What is a "critical value?"

The value of the sample statistic that marks the edge of the region of rejection in a sampling distribution; values that fall beyond it lie in the region of rejection

What is a sample distribution?

formula 1a

What are parametric and nonparametric statistics?

parametric - Inferential procedures that require certain assumptions about the parameters of the raw score population represented by the sample data; usually used with scores most appropriately described by the mean nonparametric - Inferential procedures that do not require stringent assumptions about the parameters of the raw score population represented by the sample data; usually used with scores most appropriately described by the median or the mode

What does "signifant" and "nonsignificant" mean?

significant - Describes results that are too unlikely to accept as resulting from chance sampling error when the predicted relationship does not exist; it indicates rejection of the null hypothesis nonsignificant - Describes results that are considered likely to result from chance sampling error when the predicted relationship does not exist; it indicates failure to reject the null hypothesis

What is a "standard error of the mean," and what distribution does it describe?

the standard deviation of the sampling distribution of means; used in the z- test (symbolized by Ox) and estimated in the one sample t - test (symbolized by Sx) - Ox = Ox/saure root of N - Sx = Sx / square root of N

Is the z-distribution the same as or different than the raw score distribution?

the z - distribution is always the same shape as the raw score distribution.

Why would you want to convert a raw score into a z score?

to know the location of the score on the x - axis