Phone surveys Anytime we conduct a survey, we musttake care to avoid undercoverage. Suppose we plan toselect 500 names from the city phone book, call theirhomes between noon and 4 pm, and interview whoeveranswers, anticipating contacts with at least 200 people.a) Why is it difficult to use a simple random sample here? b) Describe a more convenient, but still random, sam-pling strategy. c) What kinds of households are likely to be included inthe eventual sample of opinion? Excluded? d) Suppose, instead, that we continue calling each num-ber, perhaps in the morning or evening, until an adult is contacted and interviewed. How does this improvethe sampling design?e) Random-digit dialing machines can generate the phone calls for us. How would this improve our de-sign? Is anyone still excluded?
Addition Rule of Probability
It simply refers to the likelihood of an event taking place whenever the occurrence of an event is uncertain. The probability of a single event can be calculated by dividing the number of successful trials of that event by the total number of trials.
Expected Value
When a large number of trials are performed for any random variable ‘X’, the predicted result is most likely the mean of all the outcomes for the random variable and it is known as expected value also known as expectation. The expected value, also known as the expectation, is denoted by: E(X).
Probability Distributions
Understanding probability is necessary to know the probability distributions. In statistics, probability is how the uncertainty of an event is measured. This event can be anything. The most common examples include tossing a coin, rolling a die, or choosing a card. Each of these events has multiple possibilities. Every such possibility is measured with the help of probability. To be more precise, the probability is used for calculating the occurrence of events that may or may not happen. Probability does not give sure results. Unless the probability of any event is 1, the different outcomes may or may not happen in real life, regardless of how less or how more their probability is.
Basic Probability
The simple definition of probability it is a chance of the occurrence of an event. It is defined in numerical form and the probability value is between 0 to 1. The probability value 0 indicates that there is no chance of that event occurring and the probability value 1 indicates that the event will occur. Sum of the probability value must be 1. The probability value is never a negative number. If it happens, then recheck the calculation.
take care to avoid undercoverage. Suppose we plan to
select 500 names from the city phone book, call their
homes between noon and 4 pm, and interview whoever
answers, anticipating contacts with at least 200 people.
a) Why is it difficult to use a simple random sample here?
pling strategy.
the eventual sample of opinion? Excluded?
ber, perhaps in the morning or evening, until an adult
the sampling design?
e) Random-digit dialing machines can generate the
sign? Is anyone still excluded?
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