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Basic Concepts of Probability quiz #4

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  • How do scientists use probability when describing risks?
    They quantify the likelihood of events to assess and communicate risk.
  • What is true of covariance?
    Covariance measures the direction of the linear relationship between two variables.
  • When would you calculate an expected value?
    When you want to find the average outcome of a random variable over many trials.
  • For p(a or b) = p(a) + p(b), what must be true?
    Events a and b must be mutually exclusive.
  • What is true of statistical forecasting methods that capture historic trends?
    They use past data to predict future outcomes.
  • What is a proper way to describe the probability of flipping heads on a fair coin?
    The probability is 1/2, or 0.5, or 50%.
  • What limits the accuracy of a poll?
    Sampling error.
  • How is the addition rule of probability best described?
    The probability of either event a or b is the sum of their probabilities minus the probability of both occurring.
  • What does it mean for data to have a relationship with the answer needed?
    The data are relevant to the research question.
  • What are primary data?
    Primary data are collected directly by the researcher for a specific purpose.
  • What are the two requirements for a discrete probability distribution?
    Probabilities must be between 0 and 1, and their sum must be 1.
  • What is the difference between an outcome and an event?
    An outcome is a single result; an event is a set of outcomes.
  • How do you determine if a value is a parameter or a statistic?
    A parameter describes a population; a statistic describes a sample.
  • What is the difference between univariate and bivariate data?
    Univariate data involve one variable; bivariate data involve two variables.
  • What is meant by a marginal distribution and a conditional distribution?
    Marginal distribution is the distribution of one variable; conditional distribution is the distribution of one variable given a specific value of another.
  • Which numbers cannot be used to represent the probability of an event?
    Numbers less than 0 or greater than 1.
  • How do you determine whether a number is a statistic or a parameter?
    If it describes a sample, it is a statistic; if it describes a population, it is a parameter.
  • What are primary data?
    Primary data are collected firsthand by the researcher.
  • If the data collected are the number of traffic tickets, what is the level of measurement?
    Ratio level.
  • What are the two requirements for a discrete probability distribution?
    Probabilities must be between 0 and 1, and their sum must be 1.
  • What is the difference between relative frequency and cumulative frequency?
    Relative frequency is the proportion of times an event occurs; cumulative frequency is the sum of frequencies up to a certain point.
  • What is not a requirement of the binomial probability distribution?
    More than two possible outcomes per trial.
  • How is a sample related to a population?
    A sample is a subset of a population.
  • What are properties of the student's t-distribution?
    It is symmetric, bell-shaped, and has heavier tails than the normal distribution.
  • What is meant by a marginal distribution and a conditional distribution?
    Marginal distribution is the distribution of one variable; conditional distribution is the distribution given a condition on another variable.
  • What is the difference between an outcome and an event?
    An outcome is a single result; an event is a set of outcomes.
  • How do you determine if a value is a parameter or a statistic?
    A parameter describes a population; a statistic describes a sample.
  • What is not a voluntary response sample?
    A sample selected randomly from the population.
  • What is the difference between univariate and bivariate data?
    Univariate data involve one variable; bivariate data involve two variables.
  • What is not a level of measurement?
    Probability is not a level of measurement.
  • Which statement about probability is not true?
    Probability can be negative.
  • What must be known about a data set before using the empirical rule?
    The data should be approximately normally distributed.
  • Why is it important to be skeptical of statistical results reported in the media?
    Media reports may misrepresent data or omit important context.
  • Is valid data always reliable data?
    Not necessarily; data can be valid but not reliable, and vice versa.
  • How is error (accuracy of a poll) expressed?
    As a plus-or-minus percentage.
  • What is the Monte Carlo fallacy?
    The mistaken belief that past random events affect future outcomes.
  • Why is a sample used more often than a population?
    Because sampling is more practical and efficient.
  • What is the benefit of using inferential statistics?
    It allows researchers to make conclusions about populations from samples.
  • What is the process of finding patterns and anomalies in data to predict outcomes called?
    Data analysis or predictive analytics.
  • What is 16 out of 25 as a percentage?
    16/25 × 100 = 64%.