GRAVETTER_CH06_Introduction to Probability Flashcards
TRUE OR FALSE: Inferential procedures are typically built around the concept of probability.
TRUE.
THINK! What is the role of probability in inferential statistics?
Probability is used to predict the type of samples that are likely to be obtained from a population.
TRUE OR FALSE: We can use probabilities to make inferences of a population from a sample we obtained.
TRUE.
What is the term for any specific outcome that is defined as a fraction or a proportion of all the possible outcomes?
Probability.
What is the symbol for probability?
P, followed by the specific outcome in parentheses.
E.g. p(king) refers to the probability of selecting a king from a deck of cards
TRUE OR FALSE: All probability values are contained in a limited range, or in a range from 0-1.
TRUE.
At one extreme, when an event never occurs, the probability is zero, or 0%. At the other extreme, when the event always occurs the probability is 1, or 100%.
What type of sampling should the outcomes be obtained by for the preceding definition of probability to be accurate?
Random sampling.
TRUE OR FALSE: A random sample requires that each individual in the population has an equal chance of being selected.
TRUE.
What is the term for the sample obtained through the process of random sampling?
A simple random sample.
What type of sample requires that each individual has an equal chance of being selected and that the probability of being selected stays constant from one selection to the next if more than one individual is selected?
An independent random sample.
THINK! What are two requirements that should be considered when doing random sampling?
Equal chance and constant probability.
THINK! Why does the simple definition of probability not apply in the question of whether you will win a million dollars in the lottery, where there are only two possible alternatives: you will win or you will not win?
This is because the two alternatives are not equally likely. According to the simple algebraic definition of probability, the p of each outcome would be p=1/2, but we know that is not the actual case.
THINK! How is selecting one card (let’s say the jack of diamonds) from a deck of 52 in two chances not apply in accordance to the requirements of random sampling?
This is because the probability does not stay constant from the first trial to the next.
1st draw:
p(jack of diamonds) = 1/52
2nd draw:
p(jack of diamonds) = 1/51 if the card was not the jack of diamonds
p(jack of diamonds) = 0 if the first card was the jack of diamonds
What is the term for the sampling process used to keep the probabilities changing from one selection to the next? (Where it is necessary to return each individual to the population before you make the next selection)
Sampling with replacement.
TRUE OR FALSE: It is actually very common to define random sampling without the requirement of constant probabilities.
TRUE.
This is known as random sampling without replacement.
