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Psychological Statistics Exam 2: Probability Density Curves and Z-Scores, Exams of Statistics

A.T. Still University of Health Sciences (ATSU)Statistics

A study guide for exam #2 in the psychological statistics course (psy207), focusing on probability density curves, z-scores, and related concepts. It covers topics such as the difference between histograms and probability density curves, the effect of standard deviation on distributions, and the conversion of raw scores to z-scores. Students are expected to understand concepts like pemdas, probability formulas, and the relationship between variability and the difference between mean and raw scores.

Typology: Exams

2023/2024

Available from 04/01/2024

DrShirley
DrShirley 🇺🇸

3.3

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4.6K documents

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PSY207: Psychological Statistics - Exam #2,
Chapters 5-8
Describe a Probability Density Curve -
A SMOOTH curve (as opposed to a histogram or frequency polygon.)
What is the difference between a Histogram and a Probability Density Curve? -
Histogram: Shows frequency
PDC: Shows probability
As the Standard Deviation increases, what happens to the Distribution? -
It flattens.
How do you turn a Normal Curve into a Standard Normal Curve? -
Convert the Raw Scores into Z-Scores.
RECALL: Z-Score Formula -
(Raw Score - Mean)
--------------------------
Standard Deviation
What's the relationship between Variability and the Difference between Mean and Raw Score? -
If one if big, the other is small.
Formula for converting Z-Scores into Raw Scores? -
(Mean) + (Z-Score)(SD)
Keep PEMDAS in mind!
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PSY207: Psychological Statistics - Exam #2,

Chapters 5-

Describe a Probability Density Curve - A SMOOTH curve (as opposed to a histogram or frequency polygon.) What is the difference between a Histogram and a Probability Density Curve? - Histogram: Shows frequency PDC: Shows probability As the Standard Deviation increases, what happens to the Distribution? - It flattens. How do you turn a Normal Curve into a Standard Normal Curve? - Convert the Raw Scores into Z-Scores. RECALL: Z-Score Formula - (Raw Score - Mean)

Standard Deviation What's the relationship between Variability and the Difference between Mean and Raw Score? - If one if big, the other is small. Formula for converting Z-Scores into Raw Scores? - (Mean) + (Z-Score)(SD) Keep PEMDAS in mind!

Steps for transforming a distribution? -

  1. Transform Raw Scores into Z-Scores. Use first set of parameters.
  2. Transform those Z-Scores into new X-Values. Use second set of parameters. Probability formula - Frequency of X

Number of possibilities (N) 2 Rules about probability -

  1. Will be between 0 and 1
  2. Will never be negative For the definition of probability to be accurate, what 2 things must be true about all the Possible Observations? -
  3. Equal chance of selection
  4. Constant probability (we must use replacement) What are the first two things you have to do when finding the probability using the Unit-Table? -
  5. Sketch the normal curve.
  6. Locate and shade the target area. After you do this, what's your next move? -
  7. Use the Z-Score Formula to find the Z-Score.

As the sample size increases, what happens to variability? - It decreases. 4th Property: What does the Central Limit Theorem state? - Large sample size = Closer to normal curve Formula for finding Z-Scores for Sample Means? - (Sample Mean) - (Population Mean)

Sampling Error Define: Sampling Distributions of Means - The means of all of the possible samples. Name one important feature of the sampling distribution? - It will always end up looking close to a normal curve, even if the population you began with doesn't look normal. What is the point of hypothesis testing? - To know if a group of scores is different from another group of scores. What are the 2 reasons why we need to guard against the possibility that differences between groups aren't just a coincidence. -

  1. Variability in populations
  2. Sampling Error What are the 4 Steps in Hypothesis Testing? -
  3. State the hypothesis
  1. Determine the "critical region" for decision criteria
  2. Compute a test statistic (Z-Score)
  3. Make a decision What is meant by "null hypothesis?" - What you're testing makes no difference on the original mean. What is an "alternative hypothesis?" - What you're testing changes the original mean in some way. What if your findings support your null hypothesis? - Then you have no evidence that what you're testing has an effect on the original mean. What happens to the sampling distribution of means if your null hypothesis is true? - It will be centered around the population mean. What happens to the sampling distribution of means if your null hypothesis is false? - It will be centered around some other mean other than the population mean. Alpha (a) is the probability that _________? - You will obtain a sample mean that leads you to reject the null hypothesis. Alpha (a) is the probability of Type _____ Error? -

Beta (B) is the probability that __________? -