Psy 2113 Review Sheet One

Terms to know: Make sure that you recognize and understand these terms/concepts.

1. Random sample (Independence and equal probabilities)
2. Population
3. Sample space (the set of all possible outcomes in a probability experiment)
4. Probability distribution (all probs are greater or equal to zero - the sum of the probabilities is one.)
5. Frequency distribution (frequencies, relative frequencies, and cumulative frequencies)
6. Similarity/differences between frequency distributions and probability distributions
7. Parameter versus Statistic
8. External validity versus Internal validity
9. Dependent variable versus Independent variable
10. Extraneous variable
11. Characteristics of true experiments (isolation, cause and effect relations)
12. Scales of measurement (nominal, ordinal, interval, ratio)

Data analysis:

• Stem-and-leaf plot
• Box plot
• Measures of central tendency (mean, median, mode: when to use what)
• Measures of variability (variance, standard deviation, range)

Regression and Correlation

• Regression Line ( slope and intercept).  The regression line is the line that best fits (in the least squares sense) the data.  
• The correlation tells us how well the regression line fits the data. (-1 < r <1).  Remember that correlation does not necessarily imply causation.
• Factors that affect the correlation (range restriction, extreme groups, outliers)

Probability:

1. Computing (marginal) probabilities
2. Computing probabilities with AND
3. Computing probabilities with OR
4. Computing conditional probabilities (redefining the sample space)
5. Independence (Computing AND probabilities under independence)
6. Consider the following data; Relationship of Criminal to Victim

   	Homicide	Robbery	Assault	Total
   Stranger	12	379	727	1118
   Relative	39	106	642	787
   Unknown	18	20	57	95
   	69	505	1426	2000

P(Assault)=, P(Robbery)=, P(Homicide AND Stranger)=, P(Relative| Homicide)=.   Answers 1

Normal distributions:

• Standard normal distribution problems (p to z, and z to p)
• P(a < z < b) denotes the probability that the z score is between a and b.
• P(z > a) denotes the probability that the z score is greater than a.
• P(-2 <z < 2)=   , P(z < 2.33)= , P(1.11 < z < 2.22)=   Answers 2 
• Non-standard normal distribution problems ( p to z, and z to p)

Confidence Intervals:

•     Confidence Interval on the population mean when the population variance in known: Use Z
•     Confidence Interval for a proportion when np and nq are greater than 5: Use Z
•     Confidence Interval when the population variance is not known and the sample size is small: Use t

Studying for the test:

1. Go back over your quizzes and work some problems out of every chapter. Make sure that you understand the problems that you missed on the quizzes.

You can bring a 4" by 6" card with any information that you want on it. Good luck.

Answer 1: P(Assault)=  1426/2000     P(Robbery)= 505/2000  P(Homicide AND Stranger)=12/2000

 P(Relative| Homicide)= 39/69  

Answer 2: .9544,  .9901,  .1203