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Table of Contents
Statistics I Solved Paper 2025 2nd Annual FBISE
Q.2: Attempt any Fourteen parts.
(i) Differentiate between discrete and continuous variable.
Answer:
Discrete Variable
A variable which can assume only some specific values within a given range is called discrete variable. For e.g. Number of students in a class, Number of houses in a street, number of children in a family etc. Discrete variable is countable.
Continuous Variable
A variable which can assume any value within a given range is called a continuous variable. For example, age of persons, speed of car, temperature, height, etc. Continuous variable is measurable.
(ii) What methods are used for collection of primary data?
Answer:
The most common methods or sources of collecting primary data are:
- Questionnaires
- Surveys
- Interviews
- Polls
- E-mail & Telephone
(iii) Read the following paragraph and make the frequency distribution of number of letters in each word with one as class interval.
“Studying books is the main source of knowledge. Books are indeed never failing friends of man. For a mature mind, reading is the greatest source of pleasure and solace to distressed minds”.
Answer:
| Number of Letters (Class Interval = 1) | Frequency |
| 1 | 1 |
| 2 | 6 |
| 3 | 6 |
| 4 | 2 |
| 5 | 4 |
| 6 | 5 |
| 7 | 3 |
| 8 | 3 |
| 9 | 1 |
| 10 | 1 |
| Total | 32 words |
(iv) A student obtained the following marks in four subjects. Compute weighted arithmetic mean.
| Subject | English | Urdu | Physics | Chemistry |
| Marks (X) | 50 | 60 | 80 | 90 |
| Weight (W) | 2 | 1 | 4 | 3 |
Solution:
| Subject | Marks (X) | Weight (W) | WX |
| English | 50 | 2 | 100 |
| Urdu | 60 | 1 | 60 |
| Physics | 80 | 4 | 320 |
| Chemistry | 90 | 3 | 270 |
| ∑W=10 | ∑WX = 750 |
(v) Calculate arithmetic mean of a frequency distribution of X, if:
Solution:
(vi) Compute Geometric and Harmonic mean of: 10, 15, 20, 30
Solution:
| X | 1/X |
| 10 | 0.1 |
| 15 | 0.066 |
| 20 | 0.05 |
| 30 | 0.033 |
| ∑ (1/X) = 0.249 |
(vii) The following is a frequency distribution of the number of children born in 65 families. Find median and mode for the data:
| No. of Children (X) | 0 | 1 | 2 | 3 | 4 | 5 |
| No. of families (f) | 4 | 7 | 14 | 22 | 12 | 6 |
Solution:
| X | f | C.F |
| 0 | 4 | 4 |
| 1 | 7 | 11 |
| 2 | 14 | 25 |
| 3 | 22 | 47 |
| 4 | 12 | 59 |
| 5 | 6 | 65 |
| ∑f = n 65 |
33 falls in C.F of 47 so X = 3 is median
Mode = Maximum frequency is 22 so X = 3 is mode
(viii) If lower quartile is 20 and upper quartile is 40. Calculate semi-interquartile range and coefficient of quartile deviation.
Solution:
Quartile Deviation
Coefficient of Quartile Deviation
(ix) A student calculated mean and variance of 25 observations as 20 and 16 respectively. Compute coefficient of variation.
Solution:
Data
(x) If Median = 20 and Arithmetic mean = 22, compute the value of mode.
Solution:
Mode=3Median-2Mean
Mode=3(20)-2(22)
Mode=60-44=16
(xi) Calculate mean deviation from mean and mean coefficient of dispersion of 6, 8, 10, 12, 14
Solution:
| X | |X-Mean| |
| 6 | 4 |
| 8 | 2 |
| 10 | 0 |
| 12 | 2 |
| 14 | 4 |
| ∑X = 50 | ∑|X-Mean|=12 |
Coefficient of Mean Deviation
(xii) Compute price index numbers taking “average of first 03 years” as base.
| Year | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 |
| Price | 20 | 15 | 25 | 28 | 40 | 50 | 60 |
Solution:
Step 1: Find Base Price (Average of First 3 Years)
Prices for 2000, 2001, 2002:
| Year | Price | Price Index |
| 2000 | 20 | (20/20) 100 = 100 |
| 2001 | 15 | (15/20) 100 = 75 |
| 2002 | 25 | (25/20) 100 = 125 |
| 2003 | 28 | (28/20) 100 = 140 |
| 2004 | 40 | (40/20) 100 = 200 |
| 2005 | 50 | (50/20) 100 = 250 |
| 2006 | 60 | (60/20) 100 = 300 |
(xiii) Given that ∑p1qo = 9925, ∑poqo = 9270, ∑p1q1 = 10710, ∑poq1 = 10000. Compute Laspeyres, Paasches and Fisher’s Price Index number.
Solution:
(xiv) Differentiate between simple and composite index number.
Answer:
Simple Index
In simple index number price or quantity of a single product is taken. Simple Index can be calculated through fixed base method and chain base method.
Composite Index
In composite index, the price or quantity is taken related to multiple products. Composite index is further categorized in to unweighted composite index and weighted index.
(xv) If rxy = 0.97 and bxy = 0.82, then calculate byx.
Solution:
Taking square on both sides
(xvi) If Sx = 10, Sy = 8 and rxy = 0.75, then compute two regression coefficients Y on X and X on Y.
Solution:
Regression Coefficient Y on X
Regression Coefficient X on Y
(xvii) Describe the properties of correlation coefficient (r).
Answer:
- Symmetric Property
Correlation between X variable and Y variable and Y Variable and X variable have same meaning or:
- Free from unit of measurement
Correlation coefficient is free from unit of measurement means if data is given in kilograms or length, the answer will not be in kilograms or length.
- Independent to Origin and Scale
Correlation Coefficient is independent to origin and scale means:
- Range of Correlation Coefficient
Correlation Coefficient always lies between -1 to +1 both inclusive.
- Geometric Mean of Regression Coefficients
Correlation Coefficient is a geometric mean of two regression coefficients.
- Relation with Covariance
If X and Y are two independent variables then Cov(X, Y) = 0 but it does not mean that if Cov (X, Y) = 0 then X and Y are definitely independent.
(xviii) If the second degree parabola fitted to the data for the years 1980-87 (both inclusive) with the origin at the middle of 1983 and 1984 is Ŷ = 131.81 + 16.89X + 1.64X², the unit of X being half year, then find the trend values for 1980-87.
Solution:
| Years | X= Year – 1983.5 | X² | Ŷ = 131.81 + 16.89X | Ŷ = 131.81 + 16.89X + 1.64X² |
| 1980 | -3.5 | 12.25 | 72.695 | 224.595 |
| 1981 | -2.5 | 6.25 | 89.585 | 231.645 |
| 1982 | -1.5 | 2.25 | 106.475 | 241.975 |
| 1983 | -0.5 | 0.25 | 123.365 | 255.585 |
| 1984 | 0.5 | 0.25 | 140.255 | 272.475 |
| 1985 | 1.5 | 2.25 | 157.145 | 292.645 |
| 1986 | 2.5 | 6.25 | 174.035 | 316.095 |
| 1987 | 3.5 | 12.25 | 190.925 | 342.825 |
(xix) What is meant by irregular or random variation in time series?
Answer:
These are sudden changes occurring in a time series. These are sudden in nature that is why they cannot be explained through trends or seasonal or cyclical movements. For example, sudden change due to tsunami or earthquake etc.

Section C- (Marks 26)
Q.3: The following table shows the marks obtained by the students:
| Marks | 10—19 | 20—29 | 30—39 | 40—49 | 50—59 | 60—69 |
| f | 5 | 8 | 10 | 12 | 9 | 6 |
- Calculate the Arithmetic Mean, Median and Mode
- Compute variance, standard deviation and coefficient of skewness.
Solution:
| Income (Rs) | Frequency (f) | Class Boundaries | X | fX | fX² | C.F |
| 10—19 | 5 | 9.5—19.5 | 14.5 | 72.5 | 1051.25 | 5 |
| 20—29 | 8 | 19.5—29.5 | 24.5 | 196 | 4802 | 13 |
| 30—39 | 10 | 29.5—39.5 | 34.5 | 345 | 11902.5 | 23 |
| 40—49 | 12 | 39.5—49.5 | 44.5 | 534 | 23763 | 35 |
| 50—59 | 9 | 49.5—59.5 | 54.5 | 490.5 | 26732.25 | 44 |
| 60—69 | 6 | 59.5—69.5 | 64.5 | 387 | 24961.5 | 50 |
| 50 | 2025 | 93212.5 | ||||
| ∑f = | ∑fX = | ∑fX² = |
- Calculate the Arithmetic Mean, Median and Mode
n/2=50/2=25 so model class is 39.5—49.5
- Compute variance, standard deviation and coefficient of skewness.
Q.4 (a) Compute index numbers of prices from the following data taking 1970 as base using Arithmetic Mean as an average.
| Year | Average Price in Rupees | ||
| Firewood | Soft Coke | Kerosene Oil | |
| 1970 | 3.25 | 2.50 | 0.20 |
| 1971 | 3.44 | 2.80 | 0.22 |
| 1972 | 3.50 | 2.00 | 0.25 |
| 1973 | 3.75 | 2.50 | 0.30 |
Solution
| Years | Firewood | P.R | Soft Coke | P.R | Kerosene Oil | P.R | Sum of Price Relatives | Arithmetic Mean |
| 1970 | 3.25 | 100 | 2.5 | 100 | 0.2 | 100 | 300 | 300/3 = 100 |
| 1971 | 3.44 | 105.85 | 2.8 | 112 | 0.22 | 110 | 327.85 | 327.85/3 = 109.28 |
| 1972 | 3.5 | 107.69 | 2 | 80 | 0.25 | 125 | 312.69 | 312.69/3 = 104.29 |
| 1973 | 3.75 | 115.38 | 2.5 | 100 | 0.3 | 150 | 365.38 | 365.38/3 = 121.79 |
(b) Find regression line Y on X and Correlation Coefficient (r): n = 8, ∑X = 36, ∑Y = 152, ∑XY = 768, ∑X²=204, ∑Y²=3056
Solution
Correlation Coefficient
Regression line Y on X
Q.5 (a) Compute (i) 5-years simple moving average (ii) 4 years centered moving average.
| Year | 1990 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 | 2000 |
| Value | 20 | 23 | 26 | 29 | 23 | 29 | 31 | 27 | 38 | 34 | 33 |
Solution (i) 5-years simple moving average
| Year | Value | 5 Years M.T | 5 Years M.A |
| 1990 | 20 | ||
| 1991 | 23 | ||
| 1992 | 26 | 121 | 24.2 |
| 1993 | 29 | 130 | 26 |
| 1994 | 23 | 138 | 27.6 |
| 1995 | 29 | 139 | 27.8 |
| 1996 | 31 | 148 | 29.6 |
| 1997 | 27 | 159 | 31.8 |
| 1998 | 38 | 163 | 32.6 |
| 1999 | 34 | ||
| 2000 | 33 |
Solution (ii) 4 years centered moving average
| Year | Values | 4 Years M.T | 2 Values M.T | 4 Years M.A Centered |
| 1990 | 20 | |||
| 1991 | 23 | |||
| 20+23+26+29=98 | ||||
| 1992 | 26 | 98+101=199 | 199/8 = 24.88 | |
| 23+26+29+23=101 | ||||
| 1993 | 29 | 101+107=208 | 208/8 = 26 | |
| 26+29+23+29=107 | ||||
| 1994 | 23 | 107+112=219 | 219/8 = 27.38 | |
| 29+23+29+31=112 | ||||
| 1995 | 29 | 112+110=222 | 222/8 = 27.75 | |
| 23+29+31+27=110 | ||||
| 1996 | 31 | 110+125=235 | 235/8 = 29.38 | |
| 29+31+27+38=125 | ||||
| 1997 | 27 | 125+130=255 | 255/8 = 31.88 | |
| 31+27+38+34=130 | ||||
| 1998 | 38 | 130+132=262 | 262/8 = 32.75 | |
| 27+38+34+33=132 | ||||
| 1999 | 34 | |||
| 2000 | 33 |
(b) Fit a straight line to the following data and calculate trend values:
| Year | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 |
| Value | 60 | 65 | 80 | 73 | 97 | 105 | 93 | 111 | 117 |
Solution
| Year | Value (Y) | X | XY | X² | Trend Values Ŷ =89+7.06x |
| 2001 | 60 | -4 | -240 | 16 | 60.76 |
| 2002 | 65 | -3 | -195 | 9 | 67.82 |
| 2003 | 80 | -2 | -160 | 4 | 74.88 |
| 2004 | 73 | -1 | -73 | 1 | 81.94 |
| 2005 | 97 | 0 | 0 | 0 | 89 |
| 2006 | 105 | 1 | 105 | 1 | 96.06 |
| 2007 | 93 | 2 | 186 | 4 | 103.12 |
| 2008 | 111 | 3 | 333 | 9 | 110.18 |
| 2009 | 117 | 4 | 468 | 16 | 117.24 |
| ∑Y = 801 | ∑XY = 424 | ∑X²= 60 |






