Hypothesis Testing
HYPOTHESIS TESTING TASK
DOE PRACTICAL TEAM MEMBERS (fill
this according to your DOE practical):
1. Katrina (Thor)
2. Anwar (Iron Man)
3. Kieran (Black Widow)
4. Jun Lin (Hulk)
Since I chose Iron Man, I will use Run #2 from FRACTIONAL
factorial and Run #2 from FULL factorial.
The QUESTION
The catapult (the ones that were used in the DOE practical) manufacturer needs to determine the consistency of the products they have manufactured. Therefore they want to determine whether CATAPULT A produces the same flying distance of projectile as that of CATAPULT B.
Scope
of the test
The human factor is assumed to be negligible. Therefore different
user will not have any effect on the flying distance of projectile.
Flying distance for catapult A and catapult B is collected
using the factors below:
Arm length = 34cm
Start angle = 0 degree
Stop angle = 70 degree
Step 1: State the statistical Hypotheses:
State the null hypothesis (H0):
Catapult A produces the same flying distance of projectile as
that of Catapult B
State the alternative hypothesis (H1):
Catapult A does not produce the same flying distance of projectile as that of
Catapult B.
Step 2: Formulate an analysis plan.
Sample size is small therefore t-test will be used.
Since the sign of H1 is ≠, a two tailed test is used.
Significance level (α) used in this test is 0.05
Step 3: Calculate the test statistic
State the mean and standard deviation of sample catapult A:
Mean: 142.2
Standard Deviation: 5.14
State the mean and standard deviation of sample catapult B:
Mean: 143.2
Standard Deviation: 4.64
Compute the value of the test statistic (t):
Step 4: Make a decision based on result
Type of test:
Two-tailed test, thus critical value 0.05/2 = ± 0.025
1 – 0.025 = 0.975
Using t-distribution table, critical value of t0.975
= ±2.145
Since
-2.145 < -0.382 < 2.145, therefore -0.382 is within the accepted range,
hence H0 is accepted.
Conclusion that answer the initial question
At 0.05 significance level, Catapult A and Catapult B will
produce the same flying distance.
The conclusion gathered from the other team members is that there is no difference in the flying distance from both catapults. Thus, it can be inferred that the consistency of the products manufactured is high, and there are no quality control issues between different catapults of the same model.
Reflection
Overall, hypothesis testing is actually quite simple once you
are familiar with it. Initially, it seemed very complicated. However, with
practice it became a lot easier than it looked. I feel like it is a very
important skill, especially in analysing the validity of a claim. On a larger
scale, it can be used for analysing quality consistency in products.
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