Answer:
z(s) is in the acceptance region. We accept H₀ we did not find a significantly difference in the performance of the two machines therefore we suggest not to buy a new machine
Step-by-step explanation:
We must evaluate the differences of the means of the two machines, to do so, we will assume a CI of 95%, and as the interest is to find out if the new machine has better performance ( machine has a bigger efficiency or the new machine produces more units per unit of time than the old one) the test will be a one tail-test (to the left).
New machine
Sample mean x₁ = 25
Sample variance s₁ = 27
Sample size n₁ = 45
Old machine
Sample mean x₂ = 23
Sample variance s₂ = 7,56
Sample size n₂ = 36
Test Hypothesis:
Null hypothesis H₀ x₂ - x₁ = d = 0
Alternative hypothesis Hₐ x₂ - x₁ < 0
CI = 90 % ⇒ α = 10 % α = 0,1 z(c) = - 1,28
To calculate z(s)
z(s) = ( x₂ - x₁ ) / √s₁² / n₁ + s₂² / n₂
s₁ = 27 ⇒ s₁² = 729
n₁ = 45 ⇒ s₁² / n₁ = 16,2
s₂ = 7,56 ⇒ s₂² = 57,15
n₂ = 36 ⇒ s₂² / n₂ = 1,5876
√s₁² / n₁ + s₂² / n₂ = √ 16,2 + 1.5876 = 4,2175
z(s) = (23 - 25 )/4,2175
z(s) = - 0,4742
Comparing z(s) and z(c)
|z(s)| < | z(c)|
z(s) is in the acceptance region. We accept H₀ we did not find a significantly difference in the performance of the two machines therefore we suggest not to buy a new machine
The very hight dispersion of values s₁ = 27 is evidence of frecuent values quite far from the mean
B. We can't determine from the given information.
C. Exactly one
D. None
Step-by-step explanation:
−2(x^2 − 12x − 87); x = $87
−2(x − 6)2 + 246; x = $246
−2(x − 6)2 + 246; x = $6
Answer:
11481.4875 km
Step-by-step explanation:
Given the that :
Galapagos island and Island of Naura are on the equator
Galapagos = 90.30°W
Island of Naura = 166.56°E
Ensuring same bearing is used for both :
Island of Naura = 166.56°E = (360° - 166.56°) = 193.44°W
Hence, we can calculate the difference in the bearing of both locations :
(193.44 - 90.30)°W = 103.14°
Hence the distance between Galapagos and Island of Naura along the equator is :
(Difference in bearing / total bearing) * earth's Circumference
Earth's Circumference = 40,075km
(103.14 / 360) × 40,075
0.2865 × 40,075
= 11481.4875 km
=
y=40- 3x-3
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The question is incomplete! the complete question along with answer and step by step explanation is provided below.
Question:
A researcher records the repair cost for 8 randomly selected refrigerators. A sample mean of $57.89 and standard deviation of $23.69 are subsequently computed. Determine the 95% confidence interval for the mean repair cost for the refrigerators. Assume the population is approximately normal.
Step 1 of 2 : Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.
Step 2 of 2 : Construct the 95% confidence interval. Round your answer to two decimal places.
Given Information:
Sample mean repair cost = $57.89
Sample standard deviation = σ = $23.69
Sample size = 8
Confidence level = 95%
Required Information:
step 1: critical value = ?
step 2: 95% confidence interval = ?
Answer:
step 1: critical value = 2.365
step 2: 95% confidence interval = ($38.08, $77.70)
Step-by-step explanation:
Since the sample size is less than 30 and the standard deviation of the population is also unknown therefore, we can use the t-distribution to find the required confidence interval.
The confidence interval is given by
Where is the mean repair cost and MoE is the margin of error that is given by
Where n is the sample size, s is the sample standard deviation, and is the t-score corresponding to 95% confidence level.
The t-score corresponding to 95% confidence level is
Significance level = 1 - 0.95 = 0.05/2 = 0.025
Degree of freedom (DoF) = n - 1 = 8 - 1 = 7
From the t-table at α = 0.025 and DoF = 7
t-score = 2.365
Therefore, the critical value that should be used in constructing the confidence interval is 2.365
So the required 95% confidence interval is
Therefore, we are 95% confident that the mean repair cost for the refrigerators is within the range of ($38.08, $77.70)