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UA / Psychology / PY 211 / What are the two conditions that determine a probability distribution?

What are the two conditions that determine a probability distribution?

What are the two conditions that determine a probability distribution?


From 211 Elementary Statistical Methods (Psychology) ; Professor Souza

What are the two conditions that determine a probability distribution?

Chapter 3 & 4 Test Review

Ideas Stressed in Chapter Three:

­ Chapter Three homework is very important for Exam 2

­ Practice reading graphs (examples are lower)

­ Familiarize yourself with the terms and formats used for questions

Probability Distributions = ​A variable can take at least two different values (each possible value has a probability that it occurs; lists all possible outcomes and probabilities)

Discrete Variables ​= specific values and that cannot have values between these specific values


­ Transformation of a number into a correlating number from ­3 to 3 in order to find probability

Which of the following is an example of discrete variable?

Don't forget about the age old question of What is q enclosed equal to?


Z =  or Z =  SD

X−M σ

­ X symbolizing the score, M symbolizing the mean, and SD (or σ) symbolizing the standard deviation If you want to learn more check out What is the spanish term for sorry?


­ For example, a girl has a height of 167. Z =  ; thus z = ­.3 for probability. 10 ­ ­.3 relates to a number on the ­3 to 3 scale

From 211 Elementary Statistical Methods (Psychology) ; Professor Souza

Ideas Stressed/Re­stressed in Chapter Four:

­ Statistics =​ random variables

­ Inferential Statistics =​ procedures for drawing conclusion based on the scores collected in a research study but going beyond them; creates an educated guess for studies where it is impossible to question the entire population

What are the steps in the hypothesis testing procedure?

­ Memorize the Standard Distribution Variance Formula (Depicted below) Hypothesis Test = ​A sample statistic is the best option for making an educated guess

Summary of the five steps of the​ hypothesis­testing procedure:

1. Restate the question as a research hypothesis and a null hypothesis about the populations.

2. Determine the characteristics of the comparison distribution.

3. Determine the cutoff sample score on the comparison distribution at which the null hypothesis should be rejected.

4. Determine the sample's score on the comparison distribution.

5. Decide whether to reject the null hypothesis.

Showing the null hypothesis to be true would mean showing that there is absolutely no difference between the populations. It is always possible that there is a difference between the populations but that the difference is much smaller than the particular study was able to detect. Therefore, when a result is not extreme enough to reject the null hypothesis, the results are said to be inconclusive. We also discuss several other topics like What is the meaning of census?

Central Limit Theorem

Formula:  √nσ 

Standard Error =​ How much the sample mean would vary if we took several samples at the same size from the same sample


1. Usually just grab one sample

2. Take the z­score for this sample (distance from the mean)

Formula: z = 

x̄− M √nσ 

x̄− M

   or z =   SD 

From 211 Elementary Statistical Methods (Psychology) ; Professor Souza

Hypothesis Testing Cont.

­ Objective = ​check whether a set of data agrees with a certain prediction ­ Prediction = hypothesis → statement about a population, a guess that a parameter takes a particular numerical value or falls within a particular interval, systematic way to test claims or ideas about a population

­ A significance test uses data to summarize the evidence about a hypothesis (comparing sample statistics or point estimates of parameters) to the values predicted by the hypothesis We also discuss several other topics like Why are peppers with different colors?
If you want to learn more check out How does functionalist's view of social change occur over time?
If you want to learn more check out What is the meaning of policies?

Four Basic Steps

­ State the hypothesis

­ Set a criteria for decision (basically choose a α­level) *Has to be done before observations

­ Compute the test statistic (collect data)

­ Compare and make a decision

Happy Studying!

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