Question: During the days of coronavirus, people work most of the time from home. Many offices, schools, universities conduct their works, meetings, classes online. As a result of this new normal, it is assumed that on average, utility expenses per family (electricity, water, gas etc.) increases by 40% per month. For the verification of this assumption, four months data of percentage change of utility expenses of 10 families of similar size is given below and answer the following questions, the data is normally distributed: Percentage change of utility expenses April 33.65 37.09 29.72 33.42 38.14 34.9 37.35 38.66 22.92 34.19 May 37.19 36.61 40.35 28.19 35.19 37.43 38.03 42.99 30.22 38.8 June 37.13 36.2 43.6 35.31 33.66 28.51 37.67 20.68 38.04 38.43 July 38.84 32.17 34.9 30.17 29.63 27.14 32.17 33.46 36.72 39.64 Which statistical technique(s) will be suitable for testing this assumption? (Only write the name(s) of all possible techniques) Write tabulated value of test statistic at0.05 level of significance Write the null and alternative hypothesis for this test. Write your final conclusion about the assumption. What will be the 95% confidence interval for the average percentage change of utility expenses on the basis of given data.
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
Question: During the days of coronavirus, people work most of the time from home. Many offices, schools, universities conduct their works, meetings, classes online. As a result of this new normal, it is assumed that on average, utility expenses per family (electricity, water, gas etc.) increases by 40% per month. For the verification of this assumption, four months data of percentage change of utility expenses of 10 families of similar size is given below and answer the following questions, the data is
|
Percentage change of utility expenses |
|||||||||
April |
33.65 |
37.09 |
29.72 |
33.42 |
38.14 |
34.9 |
37.35 |
38.66 |
22.92 |
34.19 |
May |
37.19 |
36.61 |
40.35 |
28.19 |
35.19 |
37.43 |
38.03 |
42.99 |
30.22 |
38.8 |
June |
37.13 |
36.2 |
43.6 |
35.31 |
33.66 |
28.51 |
37.67 |
20.68 |
38.04 |
38.43 |
July |
38.84 |
32.17 |
34.9 |
30.17 |
29.63 |
27.14 |
32.17 |
33.46 |
36.72 |
39.64 |
- Which statistical technique(s) will be suitable for testing this assumption? (Only write the name(s) of all possible techniques)
- Write tabulated value of test statistic at0.05 level of significance
- Write the null and alternative hypothesis for this test.
- Write your final conclusion about the assumption.
- What will be the 95% confidence interval for the average percentage change of utility expenses on the basis of given data.
(1) ANOVA- One Way Classification and Completely Randomised Design are the statistical techniques will be suitable for testing this assumption.
(3) Objective: To test whether the percentage change of utility expenses in four months are significant or not.
Setting of Hypothesis:
Null Hypothesis H0 : Four months data of percentage change of utility expenses of 10 families are equal. that is, H0 : μ1 = μ2 = ... = μ10.
Alternative Hypothesis H1 : Four months data of percentage change of utility expenses of 10 families are not equal. that is, H1 : μ1 ≠ μ2≠ ... ≠ μ10.
Calculation:
Given table is as follows below:
Now, Grand Total (G) = ΣTi = 1389.11 Raw Sum of Squares (RSS) = ΣΣyij2 = 33.652 + 37.092 + 29.722 + ... + 39.642 = 49177 Correction Factor (CF) = G2/N = (1389.11)2/40 = 48240.66 Total Sum of Squares (TSS) = RSS - CF = 49177 - 48240.66 = 936.34 Treatment Sum of Squares (SST) = Σ Ti2/ni - CF= 48293.16 - 48240.66 = 52.5 Error Sum of Squares (ESS) = TSS - SST = 936.34 - 52.5 = 883.84
Construction of ANOVA Table:
If F calculated value is 0.712 at 0.05 level of significance with (3,36) degrees of freedom then the F tabulated value is 2.866.
Since, F cal = 0.712 < F tab = 2.866. Hence, null hypothesis H0 may be accepted at 5% level of significance with (3,36) degrees of freedom.
(2) The tabulated value of the test statistic is 2.866 at 0.05 level of significance.
(4) Conclusion: Therefore, from the above statistical evaluation we conclude that there is a strong evidence to accept the null hypothesis H0. That means, four months data of percentage change of utility expenses of 10 families are equal.
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