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Case study (4 Marks)

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Question 14 Marks
Read the following text and answer the following questions on the basis of the same:
A group of 7 weeks old chickens, reared on a high protein diet weight 12, 15, 11, 16, 14, 14, 16 ounces; a second group of 5 chickens, similarly treated except that they receive a low protein diet, weight 8, 10, 14, 10, 13 ounces. Given that the value of t for 10 degree of freedom at 5% level of significance is 2.23.

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Q.1. Mean weight of old chickens, reared on a high protein diet is:
(A) 14 (B) 11 (C) 98 (D) 55

Q.2. Sum of the deviations of old chickens is:
(A) 23 (C) 22 (B) 18 (D) 14

Q.3. Mean weight chickens, receive a low protein diet is:
(A) 14 (B) 11 (C) 98 (D) 55

Q.4. The standard error for given two samples is:
(A) 2.14 (B) 2.41 (C) 2.93 (D) 2.55
Answer
(1) (A) 14
Explanation: Number of terms in first group i.e. $n_1$=7
Mean weight of old chickens, reared on a high protein diet is
$\begin{aligned} \bar{x} & =\frac{\sum x}{n_1} \\ & =\frac{12+15+11+16+14+14+16}{7} \\ & =\frac{98}{7}=14\end{aligned}$

(2) (C) 22
Explanation: Sum of the squares of mean deviations of old chickens is
$\sum(x-\bar{x})^2=\left(x_1-\bar{x}\right)^2+\left(x_2-\bar{x}\right)^2+\ldots+\left(x_y-\bar{x}\right)^2$
$=(12-14)^2+(15-14)^2+(11-14)^2$$+(16-14)^2+(14-14)^2+(14-14)^2$$+(16-14)^2$
= 4 + 1 + 9 + 4 + 0 + 0 + 4
= 22

(3) (B) 11
Explanation: Number of terms in second group i.e. $n_1=5$
Mean weight chickens, receive a low protein diet is
$\begin{aligned} \bar{y} & =\frac{y}{n_1} \\ & =\frac{8+10+14+10+13}{5} \\ & =\frac{55}{5}=11\end{aligned}$

(4) (A) 2.14
Explanation: Formula for standard error is
$s=\sqrt{\frac{\sum(x-\bar{x})^2+\sum(y-\bar{y})^2}{n_1+n_2-2}}$
We already have the following values
Now, $\sum(y-\bar{y})^2=\left(y_1-\bar{y}\right)^2+\left(y_2-\bar{y}\right)^2+\ldots$$+\left(y_7-\bar{y}\right)^2$
$=(8-11)^2+(10-11)^2+(14-11)^2$$+(10-11)^2+(13-11)^2$
= 9 + 1 + 9 + 1 + 4
= 24
So,$s=\sqrt{\frac{22+24}{7+5-2}}=\sqrt{\frac{46}{10}}$
$=\sqrt{4.6}=2.14$
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Question 24 Marks
Read the following text and answer the following questions on the basis of the same:
For a random sample of 10 pigs fed on diet A, the increases in weight in pounds in a certain period were 10, 6, 16, 17, 13, 12, 8, 14, 15, 9 lbs for another random sample of 12 pigs fed on diet B, the increases in the same period were 7, 13, 22, 15, 12, 14, 18, 8, 21, 23, 10, 17 lbs

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Q.1. Mean of increases in weight on diet A is
(A) 12 pounds (B) 15 pounds (C) 20 pounds (D) 27 pounds

Q.2. Sum of square of deviation for diet B is:
(A) 120 (B) 314 (C) 150 (D) 214

Q.3. The number of degrees of freedom is:
(A) 10 (B) 12 (C) 15 (D) 20

Q.4. The standard error of this is:
(A) 4.65 (B) 4.55 (C) 46.5 (D) 4.10
Answer
(1) (A) 12 pounds
Explanation: Mean of increases in weight on diet A
$\begin{array}{l}=\bar{x}=\frac{\Sigma x}{n_1} \\ =\frac{10+6+16+17+13+12+8+14+15+9}{10} \\ =\frac{120}{10}=12 \text { pound }\end{array}$

(2) (B) 314
Explanation: Sum of squares of deviations of diet B $=\Sigma(y-\bar{y})^2$
$\begin{array}{l}\text { Here } \quad \bar{y}=\frac{\Sigma y}{n_2} \\ =\frac{7+13+22+15+12+14+18+21+23+10+17}{12} \\ =\frac{180}{12} \\ =15 \text { is pounds. } \\ \Sigma(y-\bar{y})^2=64+4+49+0+9+1+9+49 \\ =314\end{array}$

(3) (D) 20
Explanation: The number of degrees of freedom (v)
$\begin{array}{l}=n_1+n_2-2 \\ =10+12-2 \\ =20\end{array}$

(4) (A) 4.65
Explanation: : Standard error,
$\begin{aligned} s & =\sqrt{\frac{\Sigma(x-\bar{x})^2+\Sigma(y-\bar{y})^2}{n_1+n_2-2}} \\ & =\sqrt{\frac{120+314}{20}}\end{aligned}$
$\begin{array}{r}{\left[\because \Sigma(x-\bar{x})^2=120 \text { and }\right.} \\ \left.\Sigma(y-\bar{y})^2=314\right]\end{array}$
$\begin{array}{l}=\sqrt{21.7} \\ =4.65\end{array}$
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Case study (4 Marks) - Applied Maths STD 12 Science Questions - Vidyadip