PSY 3204 Exam 2

Meaning of " u "

Or

Probability

- f(x) / sample space -Predict random events -Never fixed events -Never negative - close to 1 --> more probable - close to 0 --> less probable

Meaning of " u " when upside down

And

" | " means

Given that

SD can equal any positive value

SD > 0 --> means there is some variability SD = 0 --> means there is no variability SD < 0 --> has no meaning

The standard error is the standard deviation for what type of distribution?

Sampling distribution

Additive Rule/Law

States that when two outcomes for a given event are mutually exclusive, the probability that any one of these outcomes occurs is equal to the sum of their individual probabilities p(A u B)= p(A) + p(B)

Binominal Distribution

The distribution of probabilities for each outcome of a bivariate random variable

Binominal Probability Distribution

The distribution of probabilities for each outcome of a bivariate random variable

The probability of an outcome or event is

The fraction of times an outcome is likely to occur

Scores close to the mean are located in the ________ of a normal distribution.

Body

Bayes's Law/Theorem

A mathematical formula that relates the conditional and marginal (unconditional) probabilities of two conditional outcomes that occur at random P(B/A) P(A) / P(B)

Normal Distribution

Theoretical distribution in which scores are symmetrical above/below the mean; mean/median/mode are all at the 50th percentile also known as Gaussian, symmetrical, or bell-shaped distribution 8 characteristics

T/F The SD of a binomial distribution is the square root of the variance.

True

T/F The additive rule is used to define mutually exclusive outcomes.

True

T/F The multiplicative rule is used for conditional outcomes.

False

The probability of Sam studying for an exam is p = .35. The probability of Sam studying for the exam and earning an A on the exam is p = .20. Hence, the probability of Sam earning an A on the exam, given that he has studied is:

0.57

Which of the following is a characteristic of probability?

Probability varies between 0 and 1

T/F The expected outcome is the sum of the products for each random outcome multiplied by the probability of its occurrence.

True

All of the following are true about normal distributions

-It is mathematically defined -The mean and SD can equal any value -The mean =, median and mode are all located at the 50th percentile NOT TRUE: -The distribution is asymmetrical

Conditional Probability

-Occurrence of one outcome changes the probability that the other outcome will occur - Stated that probability of one event (A), given that another event (B) occurred

Independent Outcomes

-When the probability of one outcome does not affect the probability of the second outcome -example: flipping a coin--> outcome on first flip will not affect outcome of the second flip

A bag has 10 blue chips, 10 red chips, 10 green chips, and 10 white chips. The probability of blindly picking a red and green chip in one try will be

0.06

A researcher records the number of interviews a person has to attend before landing a successful job. She finds that the probability of landing a job after one interview is p = .14; two interviews is p = .36; three interviews is p = .32; and four interviews is p = .10. What is the probability that a person lands a job after at least two interviews?

0.50

The z distribution is normally distributed with a mean of 0 and a variance of ________.

1

A researcher determines that the probability of winning of a new outcome in his experiment is p = .45. Assuming that a new and old outcome are mutually exclusive events, the probability of an old or new outcome would be

1.00

A poll showed that students had no preference among four times during which a class was offered. In this case, the probability of any specific time would be

1/4

If there are four Aces in a deck of 52 cards, then what is the probability of selecting one Ace on a single draw from the deck of cards?

4/52

The following are six random outcomes for a sample space: −.25, −.5, −.5, −.5, −.5, and −.6. What is the probability of selecting a −.5 in this example?

4/6

Bivariate Random Variable

Any random variable with only two possible outcomes; also called a dichotomous variable

Probability Distribution

Distribution of probabilities for each outcome of a random variable

T/F A binomial probability distribution is constructed for fixed variables that have at least two possible outcomes.

False

Of these, the largest proportion in a z distribution could be

The proportion of area that lies between z=+1 and z=-1

Complementary Outcomes

The sum of the probabilities for two outcomes is equal to 1. When two outcomes are complementary, they are exhaustive of all possible outcomes So the two outcomes constitute 100% of the sample space