Question

18. Given the following sample data set (30 quiz scores), answer the following questions below.

1, 3, 3, 3, 4, 4, 5, 6, 6, 7, 9, 9, 9, 9, 10, 11, 12, 14, 16, 17,

17, 17, 18, 19, 21, 23, 23, 26, 26, 27,

            18a.     Complete the grouped frequency distribution.                                   (6 points)

                                    Q20.              Q21.              Q22.  Q23.           Q24.           Q25.  

Interval         Real limits        Midpoint                f              Cf                r%                   c%

1-5                         

6-10

11-15

16-20

21-25

26-30

         Q26.  

      18b. What score is associated with the 90^th percentile?                                 (1 point)

     Q27.  

      18c. What percentage of scores fall between (and including) 16 and 25?     (1 point)

      Q28.  

      18d. What percentage of the scores are at, or below 15.5?                            (1 point)

      Q29.  

      18e. Constructing a histogram, what numbers do you use along the x-axis?

                                                                                                                              (1 point)

      Q30.  

      18f. Constructing a histogram, what is the dependent variable used to label the x-axis?

                                                                                                                                    (1 point

Answer 1

Q20-Q25.

Interval	Real limits	Mid point	f	Cf	r%	c%
1-5	0.5-5.5	3	7	7	(7/30)*100=23.33%	23.33%
6-10	5.5-10.5	8	8	15	(8/30)*100=26.67%	50%
11-15	10.5-15.5	13	3	18	(3/30)*100=10%	60%
16-20	15.5-20.5	18	6	24	(6/30)*100=20%	80%
21-25	20.5-25.5	23	3	27	(3/30)*100=10%	90%
26-30	25.5-30.5	28	3	30	(3/30)*100=10%	100%

Q26.

0.90*(N+1)=0.90*31=27.9, where, N=30

90th percentile=27th observation+0.90*(28th observation-27th observation)=23+0.9*(26-23)=25.7.

Q27. 20+10=30%

Q28. 60%.

Q29. Real limits: 0.5, 5.5, 10.5,...,30.5

Q30. Class boundary