LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
B.Com., B.B.A. DEGREE EXAMINATION – COMMERCE & COR.SECR.
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THIRD SEMESTER – November 2008
ST 3105 / ST 3102 – INTRODUCTION TO STATISTICS
Date : 11-11-08 Dept. No. Max. : 100 Marks
Time : 9:00 – 12:00
SECTION A
Answer ALL questions. (10 x 2 = 20 marks)
- What are the limitations of statistics
- State the various methods of collecting primary data.
- State any two methods of non-probability sampling.
- Distinguish between classification and tabulation.
- List the various methods of representing a frequency distribution graphically.
- Define quartile deviation.
- Positive and negative correlation.
- Pearson’s coefficient of skewness is – 0.7 and the value of the median and standard deviation are 12.8 and 6 respectively. Determine the value of the mean.
- List the various components of a time series.
- Find the regression equation of X on Y from the following data:
E x2 = 164 , Ex = 24, Ey = 44, Ey 2= 574 and Exy =306, N = 10
Find the value of X when Y = 6.
SECTION B (5 X 8 = 40 Marks)
Answer any FIVE questions
- Below is given the frequency distribution of marks in mathematics obtained by 100 students in a class
Marks | 20 – 29 | 30 – 39 | 40 – 49 | 50 – 59 | 60 – 69 | 70 – 79 | 80 – 89 | 90 -100 |
No.of students | 7 | 11 | 24 | 32 | 9 | 14 | 2 | 1 |
Draw the Ogives( “ less than “ and “ more than” type) for this distribution and use it to determine the
Median.
- Compute the geometric mean from the data given below:
Marks | 0 – 10 | 10 – 20 | 20 – 30 | 30 – 40 | 40 – 50 |
No.of students | 8 | 12 | 18 | 8 | 6 |
- The following are some particular of the distribution of weights of boys and girls in a clas.
Boys Girls
Number 100 50
Mean weight 60 kg 45 kg
Variance 9 4
Find the standard deviation of the combined data.
- Find the mean deviation about the mean for the following data:
Class Interval | 0 – 10 | 10 – 20 | 20 – 30 | 30 – 40 | 40 – 50 | 50 – 60 | 60 – 70 |
Frequency | 8 | 12 | 10 | 8 | 3 | 2 | 7 |
- The marks obtained by the students in statistics and accounts are as following
Statistics | 60 | 62 | 68 | 76 | 72 | 42 | 35 | 78 | 30 | 90 |
Accounts | 50 | 66 | 58 | 74 | 60 | 40 | 28 | 64 | 38 | 88 |
Compute the ranks for the two subjects and find the coefficient of correlation of ranks.
16.The following table gives age ( X ) in years of cars and annual maintenance cost Y (In hundred Rs.)
X | 1 | 3 | 5 | 7 | 9 |
Y | 15 | 18 | 21 | 23 | 22 |
Estimate the maintenance cost for a 4 – year old car after finding the regression equation.
- 200 candidates appeared for a competitive examination and 60 of them succeeded. 35 received
special coaching and out of them 20 candidates succeeded. Prepare a 2×2 contingency table and
using Yule’s coefficient, discuss whether special coaching is effective or not.
- Explain briefly the various methods of determining trend in the analysis of time series. Explain the
Merits and demerits of each method.
SECTION C (2 X 20 = 40 Marks)
Answer any TWO questions
- (a) The scores of two players A and B in 12 rounds are given below:
X | 74 | 75 | 78 | 72 | 78 | 77 | 79 | 81 | 79 | 76 | 72 | 71 |
Y | 87 | 84 | 80 | 88 | 89 | 85 | 86 | 82 | 82 | 79 | 86 | 80 |
Identify the better player and the more consistent player.
- (b) From the following data compute Bowley’s coefficient of skewness.
Income(Rs.) | Below 200 | 200 -400 | 400 – 600 | 600 – 800 | 800 – 1000 | 1000 above |
No.of pearsons | 25 | 40 | 85 | 75 | 16 | 16 |
- Calculate Skewness and kurtosis for the following distribution
Class Interval | 1 – 5 | 6 – 10 | 11 – 15 | 16 – 20 | 21 – 25 | 26 – 30 | 31 – 35 |
Frequency | 3 | 4 | 68 | 30 | 10 | 6 | 2 |
- (a) Calculate the correlation coefficient between X and Y from the following data:
X | 61 | 72 | 73 | 63 | 84 | 80 | 66 | 76 |
Y | 40 | 52 | 49 | 43 | 61 | 58 | 42 | 58 |
- (b) In a laboratory experiment on correlation research study, the equation of the two regression
lines Were found to be 2x – y + 1 = 0 and 3x – 2y +7 = 0. Find the mean of X and Y. Also
worked the Values of the regression coefficient of correlation between the two variables x and y.
- (a ) Calculate seasonal indices by the ratio to moving average method from the following data.
Wheat Prices ( in rupees quintal )
Quarter /Year | 1972 | 1973 | 1974 | 1975 |
I | 75 | 86 | 90 | 100 |
II | 60 | 65 | 72 | 78 |
III | 54 | 63 | 66 | 72 |
IV | 59 | 80 | 85 | 93 |
- (b) Fit a straight line trend equation by the method of least square and estimate the trend values
Year | 1961 | 1962 | 1963 | 1964 | 1965 | 1966 | 1967 | 1968 |
Value | 80 | 90 | 92 | 83 | 94 | 99 | 92 | 104 |
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