Statistical Analysis Subject
The boxplot diagram below shows the price of cars sold privately and by used cars dealers.
No 1.
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Z Test for Differences in Two Means |
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Data |
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Hypothesized Difference |
0 |
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Level of Significance |
0.05 |
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Population 1 Sample |
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Sample Size |
89 |
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Sample Mean |
15773.61798 |
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Sample Standard Deviation |
4840.665989 |
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Population 2 Sample |
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Sample Size |
32 |
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Sample Mean |
11741.1875 |
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Sample Standard Deviation |
4132.159152 |
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Intermediate Calculations |
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Difference in Sample Means |
4032.430478 |
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Standard Error of the Difference in Means |
892.6741 |
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Z Test Statistic |
4.5172 |
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Two-Tail Test |
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Lower Critical Value |
-1.9600 |
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Upper Critical Value |
1.9600 |
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p-Value |
0.00001 |
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Reject the null hypothesis |
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Upper-Tail Test |
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Upper Critical Value |
1.644853627 |
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p-Value |
0.000003 |
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Reject the null hypothesis |
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Lower-Tail Test |
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Lower Critical Value |
-1.644853627 |
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p-Value |
0.999997 |
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Do not reject the null hypothesis |
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Confidence Interval Estimate |
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for the Difference Between Two Means |
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Data |
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Confidence Level |
95.00% |
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Intermediate Calculations |
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Z Value |
1.9600 |
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Interval Half Width |
1749.609066 |
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Confidence Interval |
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Interval Lower Limit |
2282.821411 |
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Interval Upper Limit |
5782.0395 |
From the p-value =0.001>0 = a using the p-value approach, we do not reject the null hypothesis. The difference in price of the car for sale privately and for sale by a used car dealer is different than the probability of getting the difference in our sample is 0.0000000. This is a likely even. Therefore, it is proved that my sample provides actual difference in the average price of the cars of the same make and model in the specified state for sale privately and by a used car dealer.
Age of car is indicated by the price so it is positively influence price of car so I would expect the price to be dependent on the age of the care. So I am constructing a linear model with price as a dependent factor and age as independent factor to enable to predict the price from the age of car.
The scatter diagram below shows the relationship between age and price of used car. As expected this graph shows that the sample the price of the car will be high with the less age of the car. As expected, this diagram shows negative relationship and is approximately linear which does not shows positive relation between price and age.