Answer:
A) 95% confidence interval for the population mean PEF for children in biomass households = (3.214, 3.386)
95% confidence interval for the population mean PEF for children in LPG households
= (4.125, 4.375)
Simultaneous confidence interval for both = (3.214, 4.375)
B) The result of the hypothesis test is significant, hence, the true average PEF is lower for children in biomass households than it is for children in LPG households.
C) 95% confidence interval for the population mean FEY for children in biomass households = (2.264, 2.336)
Simultaneous confidence interval for both = (2.264, 4.375)
This simultaneous interval cannot be the same as that calculated in (a) above because the sample mean obtained for children in biomass households here (using FEY) is much lower than that obtained using PEF in (a).
Step-by-step explanation:
A) Confidence Interval for the population mean is basically an interval of range of values where the true population mean can be found with a certain level of confidence.
Mathematically,
Confidence Interval = (Sample mean) ± (Margin of error)
Margin of Error is the width of the confidence interval about the mean.
It is given mathematically as,
Margin of Error = (Critical value) × (standard Error of the mean)
Critical value will be obtained using the z-distribution. This is because although, there is no information provided for the population standard deviation, the sample sizes are large enough for the sample properties to approximate the population properties.
Finding the critical value from the z-tables,
Significance level for 95% confidence interval
= (100% - 95%)/2 = 2.5% = 0.025
z (0.025) = 1.960 (from the z-tables)
For the children in the biomass households
Sample mean = 3.30
Standard error of the mean = σₓ = (σ/√N)
σ = standard deviation of the sample = 1.20
N = sample size = 755
σₓ = (1.20/√755) = 0.0436724715 = 0.04367
95% Confidence Interval = (Sample mean) ± [(Critical value) × (standard Error of the mean)]
CI = 3.30 ± (1.960 × 0.04367)
CI = 3.30 ± 0.085598
95% CI = (3.214402, 3.385598)
95% Confidence interval = (3.214, 3.386)
For the children in the LPG households
Sample mean = 4.25
Standard error of the mean = σₓ = (σ/√N)
σ = standard deviation of the sample = 1.75
N = sample size = 750
σₓ = (1.75/√750) = 0.063900965 = 0.063901
95% Confidence Interval = (Sample mean) ± [(Critical value) × (standard Error of the mean)]
CI = 4.25 ± (1.960 × 0.063901)
CI = 4.25 ± 0.125246
95% CI = (4.12475404, 4.37524596)
95% Confidence interval = (4.125, 4.375)
Simultaneous confidence interval for both = (3.214, 4.375)
B) The null hypothesis usually goes against the claim we are trying to test and would be that the true average PEF for children in biomass households is not lower than that of children in LPG households.
The alternative hypothesis confirms the claim we are testing and is that the true average PEF is lower for children in biomass households than it is for children in LPG households.
Mathematically, if the true average PEF for children in biomass households is μ₁, the true average PEF for children in LPG households is μ₂ and the difference is μ = μ₁ - μ₂
The null hypothesis is
H₀: μ ≥ 0 or μ₁ ≥ μ₂
The alternative hypothesis is
Hₐ: μ < 0 or μ₁ < μ₂
Test statistic for 2 sample mean data is given as
Test statistic = (μ₂ - μ₁)/σ
σ = √[(s₂²/n₂) + (s₁²/n₁)]
μ₁ = 3.30
n₁ = 755
s₁ = 1.20
μ₂ = 4.25
n₂ = 750
s₂ = 1.75
σ = √[(1.20²/755) + (1.75²/750)] = 0.07740
z = (3.30 - 4.25) ÷ 0.07740 = -12.27
checking the tables for the p-value of this z-statistic
Significance level = 0.01
The hypothesis test uses a one-tailed condition because we're testing in only one direction.
p-value (for z = -12.27, at 0.01 significance level, with a one tailed condition) = < 0.000000001
The interpretation of p-values is that
When the p-value > significance level, we fail to reject the null hypothesis and when the p-value < significance level, we reject the null hypothesis and accept the alternative hypothesis.
Significance level = 0.01
p-value = 0.000000001
0.000000001 < 0.01
Hence,
p-value < significance level
This means that we reject the null hypothesis, accept the alternative hypothesis & say that true average PEF is lower for children in biomass households than it is for children in LPG households.
C) For FEY for biomass households,
Sample mean = 2.3 L/s
Standard error of the mean = σₓ = (σ/√N)
σ = standard deviation = 0.5
N = sample size = 755
σₓ = (0.5/√755) = 0.0182
95% Confidence Interval = (Sample mean) ± [(Critical value) × (standard Error of the mean)]
CI = 2.30 ± (1.960 × 0.0182)
CI = 2.30 ± 0.03567
95% CI = (2.264, 2.336)
Simultaneous confidence interval for both = (2.264, 4.375)
This simultaneous interval cannot be the same as that calculated in (a) above because the sample mean obtained for children in biomass households here (using FEY) is much lower than that obtained using PEF in (a).
Hope this Helps!!!