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| 1 | +--- |
| 2 | +title: Week 4 Statistics Graded Assignment Questions |
| 3 | +weight: 12 |
| 4 | +tags: |
| 5 | +- statistics |
| 6 | +categories: |
| 7 | +- Statistics Graded Assignment |
| 8 | +series: |
| 9 | +- Statistics Graded Assignment |
| 10 | +--- |
| 11 | + |
| 12 | +### Questions (1)–(6): Based on Table 4.1.G |
| 13 | + |
| 14 | +| Dealer's Location | OnePlus | BBK Electronics | |
| 15 | +| :-- | :-- | :-- | |
| 16 | +| Chennai | a | b | |
| 17 | +| Punjab | c | d | |
| 18 | +| Chennai | e | f | |
| 19 | +| Punjab | g | h | |
| 20 | +| Chennai | i | j | |
| 21 | +| Punjab | k | l | |
| 22 | +| Chennai | m | n | |
| 23 | + |
| 24 | +#### 1. What is the population standard deviation of sales of OnePlus? (Enter the answer correct to 2 decimal accuracy) |
| 25 | + |
| 26 | +{{< math/calc3 a=10 b=5 c=3 d=5 e=5 f=5 g=5 h=5 i=5 j=5 k=5 l=5 m=5 n=5 formula="a+b+c+d+e+f+g+h+i+j+k+l+m+n / 2" >}} |
| 27 | + |
| 28 | +**Solution:** |
| 29 | +Let $m_x$ and $\sigma_x$ be the mean and population standard deviation of sales of OnePlus respectively. |
| 30 | + |
| 31 | +$$ |
| 32 | +m_x = \frac{a+c+e+g+i+k+m}{7} |
| 33 | +$$ |
| 34 | + |
| 35 | +$$ |
| 36 | +\sigma_x^2 = \frac{(a - m_x)^2 + (c - m_x)^2 + (e - m_x)^2 + (g - m_x)^2 + (i - m_x)^2 + (k - m_x)^2 + (m - m_x)^2}{7} |
| 37 | +$$ |
| 38 | + |
| 39 | +Therefore, Population standard deviation of sales of OnePlus = $\sqrt{\sigma_x^2}$ |
| 40 | + |
| 41 | +{{< math/calc3 a=10 b=5 formula="a + b * 2" >}} |
| 42 | + |
| 43 | +{{< math/calc3 x=2 y=3 z=4 formula="x * y + z" >}} |
| 44 | + |
| 45 | +--- |
| 46 | + |
| 47 | +#### 2. What is the sample standard deviation of sales of BBK Electronics? (Enter the answer correct to 2 decimal accuracy) |
| 48 | + |
| 49 | +**Solution:** |
| 50 | +Let $m_y$ and $S_y$ be the mean and sample standard deviation of sales of BBK Electronics respectively. |
| 51 | + |
| 52 | +$$ |
| 53 | +m_y = \frac{b+d+f+h+j+l+n}{7} |
| 54 | +$$ |
| 55 | + |
| 56 | +$$ |
| 57 | +S_y^2 = \frac{(b - m_y)^2 + (d - m_y)^2 + (f - m_y)^2 + (h - m_y)^2 + (j - m_y)^2 + (l - m_y)^2 + (n - m_y)^2}{7-1} |
| 58 | +$$ |
| 59 | + |
| 60 | +Therefore, Standard deviation of sales of BBK Electronics = $\sqrt{S_y^2}$ |
| 61 | + |
| 62 | +--- |
| 63 | + |
| 64 | +#### 3. What is the sample co-variance between the sales of OnePlus and BBK Electronics? (Enter the answer correct to 2 decimal accuracy) |
| 65 | + |
| 66 | +**Solution:** |
| 67 | +Let $X$ = Sales of OnePlus |
| 68 | +$Y$ = Sales of BBK Electronics. |
| 69 | + |
| 70 | +$$ |
| 71 | +Cov(X,Y) = \frac{\sum_{i=1}^{7}(x_i - m_x)(y_i - m_y)}{7-1} |
| 72 | +$$ |
| 73 | + |
| 74 | +$$ |
| 75 | += \frac{(a - m_x)(b - m_y) + (c - m_x)(d - m_y) + (e - m_x)(f - m_y) + (g - m_x)(h - m_y) + (i - m_x)(j - m_y) + (k - m_x)(l - m_y) + (m - m_x)(n - m_y)}{6} |
| 76 | +$$ |
| 77 | + |
| 78 | +--- |
| 79 | + |
| 80 | +#### 4. What is the correlation coefficient between the sales of OnePlus and BBK Electronics? (Enter the answer correct to 2 decimal accuracy) |
| 81 | + |
| 82 | +**Solution:** |
| 83 | +Let $r$ be the correlation coefficient between the sales of OnePlus and BBK Electronics. |
| 84 | + |
| 85 | +$$ |
| 86 | +r = \frac{Cov(X,Y)}{S_x \times S_y} |
| 87 | +$$ |
| 88 | + |
| 89 | +where, |
| 90 | +Cov(X,Y) = Sample Covariance between sales of OnePlus and BBK Electronics. |
| 91 | +$S_x$ = Sample standard deviation of sales of OnePlus = $\sqrt{\frac{n}{n-1}} \sigma_x$ = $\sqrt{\frac{7}{6}} \sigma_x$ |
| 92 | +$S_y$ = Sample standard deviation of sales of BBK Electronics. |
| 93 | + |
| 94 | +--- |
| 95 | + |
| 96 | +#### 5. What can you say about the linear relationship between the sales of OnePlus and BBK Electronics? (More than one option can be correct) |
| 97 | + |
| 98 | +(a) Strong |
| 99 | +(b) Positive |
| 100 | +(c) Weak |
| 101 | +(d) Negative |
| 102 | +(e) Absence of linear relationship |
| 103 | +(f) Moderate |
| 104 | + |
| 105 | +**Solution:** |
| 106 | + |
| 107 | +- If $0.75 \leq r \leq 1$, then there is a strong and positive linear relationship. |
| 108 | +- If $0.5 < r < 0.75$, then there is a moderate and positive linear relationship. |
| 109 | +- If $0.25 < r < 0.5$, then there is a weak and positive linear relationship. |
| 110 | +- If $-0.25 < r < 0.25$, then there is absence of linear relationship. |
| 111 | +- If $-0.5 < r < -0.25$, then there is a weak and negative linear relationship. |
| 112 | +- If $-0.75 < r < -0.5$, then there is a moderate and negative linear relationship. |
| 113 | +- If $-1 < r < -0.75$, then there is a strong and negative linear relationship. |
| 114 | + |
| 115 | +--- |
| 116 | + |
| 117 | +#### 6. Is the sales of OnePlus strongly influenced by the location of dealer? |
| 118 | + |
| 119 | +(a) Yes |
| 120 | +(b) No |
| 121 | + |
| 122 | +**Solution:** |
| 123 | +Let Chennai be represented by 0 and Punjab by 1. |
| 124 | +The Point Bi-serial correlation coefficient between the sales of OnePlus and the location of dealer is given by: |
| 125 | + |
| 126 | +$$ |
| 127 | +r_{pb} = \frac{(\bar{Y_0} - \bar{Y_1})}{\sigma_x} \times \sqrt{p_0 \times p_1} |
| 128 | +$$ |
| 129 | + |
| 130 | +where, |
| 131 | +$p_0$ = Proportion of Chennai dealers = $\frac{4}{7}$ |
| 132 | +$p_1$ = Proportion of Punjab dealers = $\frac{3}{7}$ |
| 133 | +$\bar{Y_0}$ = Mean sales of OnePlus in Chennai = $\frac{a+e+i+m}{4}$ |
| 134 | +$\bar{Y_1}$ = Mean sales of OnePlus in Punjab = $\frac{c+g+k}{3}$ |
| 135 | +$\sigma_x$ = Population standard deviation of sales of OnePlus |
| 136 | + |
| 137 | +$$ |
| 138 | +r_{pb} = \frac{(\bar{Y_0} - \bar{Y_1})}{\sigma_x} \times 0.49487 |
| 139 | +$$ |
| 140 | + |
| 141 | +If $0.75 \leq |r_{pb}| \leq 1$, then the sales of OnePlus is strongly influenced by the location of dealer. |
| 142 | +Else, the sales of OnePlus is not strongly influenced by the location of dealer. |
| 143 | + |
| 144 | +--- |
| 145 | + |
| 146 | +### Questions (7)–(11): Based on Table 4.2.G |
| 147 | + |
| 148 | +| Economic Conditions | Bright | Average | Dull | Borderline | |
| 149 | +| :-- | :-- | :-- | :-- | :-- | |
| 150 | +| Good | a | b | c | d | |
| 151 | +| Poor | e | f | g | h | |
| 152 | + |
| 153 | +#### 7. What proportion of total students are dull? (Enter the answer correct to 2 decimal accuracy) |
| 154 | + |
| 155 | +**Solution:** |
| 156 | +Proportion of dull students = $\frac{c+g}{a+b+c+d+e+f+g+h}$ |
| 157 | + |
| 158 | +--- |
| 159 | + |
| 160 | +#### 8. What proportion of total students are poor economic conditions? (Enter the answer correct to 2 decimal accuracy) |
| 161 | + |
| 162 | +**Solution:** |
| 163 | +Proportion of students having poor economic conditions = $\frac{e+f+g+h}{a+b+c+d+e+f+g+h}$ |
| 164 | + |
| 165 | +--- |
| 166 | + |
| 167 | +#### 9. What proportion of students of good economic conditions are borderline? (Enter the answer correct to 2 decimal accuracy) |
| 168 | + |
| 169 | +**Solution:** |
| 170 | +Required proportion = $\frac{d}{a+b+c+d}$ |
| 171 | + |
| 172 | +--- |
| 173 | + |
| 174 | +#### 10. What percentage of bright students are in poor economic conditions? (Enter the answer correct to 2 decimal accuracy) |
| 175 | + |
| 176 | +**Solution:** |
| 177 | +Required percentage = $(\frac{e}{a+e}) \times 100$ |
| 178 | + |
| 179 | +--- |
| 180 | + |
| 181 | +#### 11. What percentage of average students are in good economic conditions? (Enter the answer correct to 2 decimal accuracy) |
| 182 | + |
| 183 | +**Solution:** |
| 184 | +Required percentage = $(\frac{b}{b+f}) \times 100$ |
| 185 | + |
| 186 | +--- |
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