what is the difference between moderate outliers and extreme outliers?
Moderate outliers are data points that fall outside of the typical range of values but are not significantly far from the rest of the data. Extreme outliers, on the other hand, are data points that are very far from the rest of the data and can significantly affect the overall analysis. In other words, moderate outliers are less influential than extreme outliers.
criteria for distinguishing them?
The criteria for distinguishing moderate outliers and extreme outliers can vary depending on the context of the data being analyzed. However, a common method for identifying outliers is to use the interquartile range (IQR).
The IQR is the range between the 25th percentile (Q1) and the 75th percentile (Q3) of the data. Any data points that fall below Q1 - 1.5 x IQR or above Q3 + 1.5 x IQR are considered outliers.
Based on this criterion, data points that fall between Q1 - 1.5 x IQR and Q3 + 1.5 x IQR are considered moderate outliers, while those that fall beyond this range are considered extreme outliers.
However, it's important to note that the criteria for distinguishing outliers can vary depending on the specific analysis being conducted and the nature of the data being analyzed.
621
1611
1072
1040
772.5
768
602
815
920
980
1130
1120.5
969
783
730
1500
885
871
871
781
875
1020.5
850
832
828
1380
925
851
815
685
1586
1365
1310
960
925
815
690
830
1900
790
830
781
720
682
1017
630
592.5
810
1000
725
Using the interquartile range (IQR) method, we can calculate the outliers for this dataset.
First, we need to calculate the quartiles:
Q1 = 782.75
Q3 = 1072.5
IQR = Q3 - Q1 = 289.75
Next, we can identify any data points that fall below Q1 - 1.5 x IQR or above Q3 + 1.5 x IQR:
Moderate outliers:
Extreme outliers:
The moderate outliers are those that fall between Q1 - 1.5 x IQR and Q3 + 1.5 x IQR, while the extreme outliers are those that fall beyond this range.
which of the central tendencies would best describe the above numbers and why?
To determine which central tendency best describes a dataset, we need to consider the nature of the data and the purpose of the analysis.
If the data is relatively symmetric and there are no significant outliers, the mean would be a good measure of central tendency. The mean is calculated by adding up all the values and dividing by the number of values.
However, if the data is skewed or contains outliers, the median may be a better measure of central tendency. The median is the middle value when the data is arranged in order from smallest to largest.
Looking at the data provided, we can see that there are some outliers present. Therefore, the median is likely a better measure of central tendency than the mean.
The median of the dataset is 850, which means that half of the values are above 850 and half are below. This is a good measure of central tendency because it is not affected by extreme values like the mean can be.
Estimate the 95% confidence interval for the population mean of the above numbers and interpret your results.
To estimate the 95% confidence interval for the population mean of the above numbers, we can use the following formula:
Confidence Interval = sample mean ± (t-value) x (standard error)
Where:
First, we need to calculate the sample mean and standard deviation:
x̄ = (sum of values) / n = 924.82
s = square root of [(sum of (xi - x̄)^2) / (n-1)] = 295.13
Next, we need to calculate the t-value. Since the sample size is 45, the degrees of freedom are n-1 = 44. Using a t-distribution table or calculator, we find that the critical value for a two-tailed test with a confidence level of 95% is 2.02 (rounded to two decimal places).
Now we can calculate the standard error:
standard error = s / √n = 44.08
Finally, we can calculate the confidence interval:
Confidence Interval = 924.82 ± 2.02 x 44.08
Confidence Interval = (837.33, 1012.31)
This means that we are 95% confident that the true population mean falls somewhere between 837.33 and 1012.31. In other words, if we were to repeat this sampling process many times and calculate a different confidence interval each time, 95% of those intervals would contain the true population mean.
Interpreting the results, we can say that there is a high degree of certainty that the true population mean lies within this interval. This can be useful for making inferences about the population based on the sample data.
Do you make any assumptions for the estimation? Explain why?
Yes, there are a few assumptions that we need to make in order to use the formula for estimating the confidence interval for the population mean:
The sample is a random sample from the population of interest: This means that each member of the population has an equal chance of being selected for the sample. If the sample is not random, it may not be representative of the population and the results may not be accurate.
The sample size is large enough: In general, the sample size should be at least 30 for the Central Limit Theorem to apply. With a sample size of 45, we can assume that the sample is large enough for our purposes.
The data follows a normal distribution or the sample size is large enough for the Central Limit Theorem to apply: If the data is not normally distributed and the sample size is small, the t-distribution may not be appropriate for calculating the confidence interval. However, with a sample size of 45, we can assume that the Central Limit Theorem applies and the distribution of sample means is approximately normal.
The sample standard deviation is a good estimate of the population standard deviation: In general, the sample standard deviation should be a good estimate of the population standard deviation. If the sample standard deviation is not a good estimate of the population standard deviation, the margin of error may be too large or too small.
Therefore, we are assuming that the sample is representative of the population, the sample size is large enough, the data is normally distributed or the Central Limit Theorem applies, and the sample standard deviation is a good estimate of the population standard deviation. If any of these assumptions are not met, the results may not be accurate.
interpret the formula: confidence interval = X ̅±Z σ/√n
The formula for the confidence interval is used to estimate a range of values that is likely to contain the true population mean with a certain level of confidence. The formula is:
Confidence interval = X̄ ± Z(σ/√n)
Where:
The formula works by taking the sample mean (X̄) and adding and subtracting a margin of error (Z(σ/√n)) to create a range of values that is likely to contain the true population mean with a certain level of confidence.
The critical value of the normal distribution (Z) depends on the desired level of confidence. For example, if we want a 95% confidence interval, the critical value would be 1.96. If we want a 99% confidence interval, the critical value would be 2.58.
The standard deviation (σ) is a measure of how spread out the data is. If the population standard deviation is known, we can use it in the formula. If it is unknown, we can use the sample standard deviation (s) as an estimate.
The sample size (n) is important because as the sample size increases, the margin of error decreases and the confidence interval becomes narrower. Therefore, larger sample sizes generally lead to more precise estimates.
In summary, the formula for the confidence interval is a useful tool for estimating the range of values that is likely to contain the true population mean with a certain level of confidence, based on a sample from the population. It takes into account the sample mean, the standard deviation, the sample size, and the desired level of confidence to create a range of values that can be used to make inferences about the population.
given the following information:
the population mean = $937.24
(1-α)*100%=95% ⇒ α=0.05 Z=1.96
σ= 278.3078651 ~278.31
n=50.
calculate the confidence interval
Using the formula for the confidence interval:
Confidence interval = X̄ ± Z(σ/√n)
We can plug in the given values:
Confidence interval = $937.24 ± 1.96(278.31/√50)
Calculating the standard error:
standard error = σ/√n = 278.31/√50 = 39.34
Now we can substitute the values:
Confidence interval = $937.24 ± 1.96(39.34)
Calculating the values inside the parentheses:
1.96(39.34) ≈ 77.06
Now we can substitute the value:
Confidence interval = $937.24 ± 77.06
Simplifying:
Lower limit = $860.18
Upper limit = $1014.30
Therefore, the 95% confidence interval for the population mean is approximately $860.18 to $1014.30. This means that if we were to repeat this sampling process many times and calculate a different confidence interval each time, 95% of those intervals would contain the true population mean. We can be 95% confident that the true population mean lies somewhere within this interval.
House price ($'000) house size (m2) No. of bedrooms
Mean 937.24 660.634 3.22
Median 850.5 601.5 3
Mode 815 620 3
interpret the central tendency of House price, house size and No. of bedrooms based on above numbers.