Answer:
Part A
b. 14.6 ± 7.38
Part B
b. 3.43
Part C
a. P-value < 0.01
Part D
b. There is sufficient evidence to reject the null hypothesis
Step-by-step explanation:
Part A
The given data are;
The number of seedlings in the field = 20
The number of seedlings selected to receive herbicide A = 10
The number of seedlings selected to receive herbicide B = 10
The height in centimeters of seedlings treated with Herbicide A,
= 94.5 cm
The standard deviation, s₁ = 10 cm
The height in centimeters of seedlings treated with Herbicide B,
= 109.1 cm
The standard deviation, s₂ = 9 cm
The 90% confidence interval for μ₂ - μ₁, is given as follows;
![\left (\bar{x}_{2}- \bar{x}_{1} \right )\pm t_{\alpha /2}\sqrt{\dfrac{s_{1}^{2}}{n_{1}}+\dfrac{s_{2}^{2}}{n_{2}}}](https://tex.z-dn.net/?f=%5Cleft%20%28%5Cbar%7Bx%7D_%7B2%7D-%20%5Cbar%7Bx%7D_%7B1%7D%20%20%5Cright%20%29%5Cpm%20t_%7B%5Calpha%20%2F2%7D%5Csqrt%7B%5Cdfrac%7Bs_%7B1%7D%5E%7B2%7D%7D%7Bn_%7B1%7D%7D%2B%5Cdfrac%7Bs_%7B2%7D%5E%7B2%7D%7D%7Bn_%7B2%7D%7D%7D)
The critical-t at 95% and n₁ + n₂ - 2 degrees of freedom is given as follows;
The degrees of freedom, df = n₁ + n₂ - 2 = 10 + 10 - 2 = 18
α = 100% - 90% = 10%
∴ For two tailed test, we have, α/2 = 10%/2 = 5% = 0.05
= 1.734
![C.I. = \left (109.1- 94.5 \right )\pm 1.734 \times \sqrt{\dfrac{10^{2}}{10}+\dfrac{9^{2}}{10}}](https://tex.z-dn.net/?f=C.I.%20%3D%20%5Cleft%20%28109.1-%2094.5%20%5Cright%20%29%5Cpm%201.734%20%5Ctimes%20%5Csqrt%7B%5Cdfrac%7B10%5E%7B2%7D%7D%7B10%7D%2B%5Cdfrac%7B9%5E%7B2%7D%7D%7B10%7D%7D)
C.I. ≈ 14.6 ± 7.37714603353
The 90% C.I. ≈ 14.6 ± 7.38
b. 14.6 ± 7.38
Part B
With the hypotheses are given as follows;
H₀; μ₂ - μ₁ = 0
Hₐ; μ₂ - μ₁ ≠ 0
The two sample t-statistic is given as follows;
![t=\dfrac{(\bar{x}_{2}-\bar{x}_{1})}{\sqrt{\dfrac{s_{1}^{2} }{n_{1}}+\dfrac{s _{2}^{2}}{n_{2}}}}](https://tex.z-dn.net/?f=t%3D%5Cdfrac%7B%28%5Cbar%7Bx%7D_%7B2%7D-%5Cbar%7Bx%7D_%7B1%7D%29%7D%7B%5Csqrt%7B%5Cdfrac%7Bs_%7B1%7D%5E%7B2%7D%20%7D%7Bn_%7B1%7D%7D%2B%5Cdfrac%7Bs%20_%7B2%7D%5E%7B2%7D%7D%7Bn_%7B2%7D%7D%7D%7D)
![t-statistic=\dfrac{(109.1-94.5)}{\sqrt{\dfrac{10^{2} }{10}+\dfrac{9^{2}}{10}}} \approx 3.43173361147](https://tex.z-dn.net/?f=t-statistic%3D%5Cdfrac%7B%28109.1-94.5%29%7D%7B%5Csqrt%7B%5Cdfrac%7B10%5E%7B2%7D%20%7D%7B10%7D%2B%5Cdfrac%7B9%5E%7B2%7D%7D%7B10%7D%7D%7D%20%5Capprox%203.43173361147)
The two sample t-statistic ≈ 3.43
b. 3.43
Part C
From the t-table, the p-value, we have, the p-value < 0.01
a. P-value < 0.01
Part D
Given that a significance level of 0.05 level is used and the p-value of 0.01 is less than the significance level, there is enough statistical evidence to reject the null hypothesis
b. There is sufficient evidence to reject the null hypothesis.