Lisa looked at a frequency distribution of the travel time of some workers. The distribution has five classes. She would like to compute the mean travel time. Which of the following statements is TRUE?Group of answer choicesThe sample size is 5.All values in a class are estimated to be equal to the class mid-point.Averages like mean and median cannot be computed for grouped data.She needs to know the standard deviation before computing the mea
Question
Lisa looked at a frequency distribution of the travel time of some workers. The distribution has five classes. She would like to compute the mean travel time. Which of the following statements is TRUE?Group of answer choicesThe sample size is 5.All values in a class are estimated to be equal to the class mid-point.Averages like mean and median cannot be computed for grouped data.She needs to know the standard deviation before computing the mea
Solution
The statement that is true is: "All values in a class are estimated to be equal to the class mid-point."
When computing the mean for grouped data, it is common to use the mid-point of each class as a representative value for the observations within that class. This is because the exact values within each class are not known, so the mid-point is a reasonable estimate.
The sample size is not necessarily 5 just because there are five classes. The sample size refers to the number of observations, not the number of classes.
Averages like mean and median can indeed be computed for grouped data, although the calculations are a bit different than for ungrouped data.
Finally, the standard deviation is not needed to compute the mean. The standard deviation is a measure of the spread of the data, while the mean is a measure of central tendency. They are separate statistical measures.
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