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Descriptive stats for psych
The document provides descriptive statistics for hours studied for an exam by 40 students. It includes a tally table showing the hours studied and frequency, as well as calculations for the total hours studied, mean, median, and mode. The mean was 5.6 hours. The median was the middle number of the data arranged in ascending order. The mode was the number that appeared most often in the tally table, which was 6 hours studied. A second table shows sample grades for a quiz and asks to calculate the mean, median, and mode, and draw a histogram to determine if the data is normally, negatively, or positively skewed.
Descriptive stats for psych
- 1. Descriptive Statistics forPsychology
- 2. Hours Studied Tally Frequency Total Hours Studied 10 I 1 10 9 III 3 27 8 IIII 4 32 7 IIII 5 35 6 IIII III 8 48 5 IIII II 7 35 4 IIII 5 20 3 IIII 4 12 2 II 2 4 1 I 1 1 0 0 N=40 ∑ = 224 Total hours studied = Hours studied X frequency
- 3. The mean, thearithmetic average of all scores under consideration, is computed by dividing the sum of the scores by the number of scores. 224 = 5.6 = mean number of hours studied for the exam 40
- 4. The median isthe point at which 50% of the observations fall below and 50% above or, in other words, the middle number of a 10 set of numbers arranged in ascending or 9 descending order. 8 7 6 5 4 3 2 1 0
- 5. The mode isthe number that appears most often Hours Studied Frequency 10 1 What is the Mode 9 3 according to this table? 8 4 7 5 6 8 5 7 4 5 3 4 2 2 1 1 0 0
- 6.
- 8. negative positive
- 9. Now it’s yourturn! Descriptive Statistics Activity Below is a random sample of grades from a recent quiz. 90, 60, 65, 70, 85, 95, 50, 80, 70, 60, 50, 65, 75, 80, 85, 70, 65, 55, 100, 65, 70, 85, 80, 65, 75 1. Calculate the Mean, median, and mode. a. Create a histogram. b. Is the data normal, negatively, or positively skewed?
- 10. Tally Score Frequency total I 100 1 100 I 95 1 95 I 90 1 90 III 85 3 255 III 80 3 240 II 75 2 150 IIII 70 4 280 IIIII 65 5 325 II 60 2 120 I 55 1 55 II 50 2 100
- 11. MEDIAN? MODE? 100 100 95 95 90 90 85 85 85 85 85 85 80 80 80 80 80 80 75 75 75 75 70 70 70 <- 70 70 70 70 70 65 65 65 65 65 65 65 65 65 65 60 60 60 60 55 55 50 50 50 50
Editor's Notes
- #2 Descriptive statistics employs a set of procedures that make it possible to meaningfully and accurately summarize and describe samples of data. In order for one to make meaningful statements about psychological events, the variable or variables involved must be organized, measured, and then expressed as quantities. Such measurements are often expressed as measures of central tendency and measures of variability.
- #5 What is the median? (6)
- #6 The mode is also 6
- #7 The frequency (number of students) determined from the tally is the ordinate (vertical, or Y, axis), and the number of hours studied is the abscissa (horizontal, or X, axis). Each one-hour interval is presented sequentially, and the height of each bar represents the number of students who studied that number of hours.
- #8 Frequency polygons are graphs in which the frequency of occurrence of the variable measured is shown by using connected points rather than bars. Figure 2 shows, in a frequency polygon, the same data displayed in Figure 1 . (Note that if the midpoints of each of the bars in Figure 1 were connected, the result would be this frequency polygon.)
- #9 if enough measures are taken of a variable and plotted as a frequency polygon, the result is a normal curve (bell-shaped curve), or normal distribution (a)Skewed distributions are asymmetrical, with most of the scores grouped toward one end. The mean, median, and mode fall at different points. Distributions may be skewed to the left ( negatively skewed) (Figure 3 b) or to the right ( positively skewed) (Figure 3 c).This distribution has a negative skew. The median is larger than the mean.This distribution has a positive skew. Note that the mean is larger than the median.