The mean and standard deviation of 40 observations are 30 and 5 respectively. It was noticed that two of these observations 12 and 10 were wrongly recorded. If σ is the standard deviation of the data after omitting the two wrong observations from the data, then 38σ2 is equal to ______.
The mean and standard deviation of 40 observations are 30 and 5 respectively. It was noticed that two of these observations 12 and 10 were wrongly recorded. If σ is the standard deviation of the data after omitting the two wrong observations from the data, then 38σ2 is equal to ______.
Correct Answer: 238
Solution and Explanation
The correct answer is 238
\(μ=\frac{∑x_i}{40}=30 ⇒∑x_i=1200\)
\(σ^2=\frac{∑x^{2}_{i}}{40}−(30)2=25 ⇒ ∑x_{i}^{2}=37000\)
After omitting two wrong observations
\(∑y_i=1200−12−10=1178\)
\(∑y_{i}^{2}=37000−144−100=36756\)
Then,
\(σ^2=\frac{∑y_{i}^{2}}{38}−(\frac{∑y_i}{38})^2\)
\(=\frac{36756}{38}−(\frac{1178}{38})^2=−31^2\)
\(38σ^2=36756–36518=238\)
Top Questions on Statistics
Consider the following frequency distribution:
Value 4 5 8 9 6 12 11 Frequency 5 $ f_1 $ $ f_2 $ 2 1 1 3 Suppose that the sum of the frequencies is 19 and the median of this frequency distribution is 6.
For the given frequency distribution, let:
- $ \alpha $ denote the mean deviation about the mean
- $ \beta $ denote the mean deviation about the median
- $ \sigma^2 $ denote the variance
Match each entry in List-I to the correct entry in List-II and choose the correct option.
List-I
- (P) $ 7f_1 + 9f_2 $ is equal to
- (Q) $ 19\alpha $ is equal to
- (R) $ 19\beta $ is equal to
- (S) $ 19\sigma^2 $ is equal to
List-II
- (1) 146
- (2) 47
- (3) 48
- (4) 145
- (5) 55
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Concepts Used:
Statistics
Statistics is a field of mathematics concerned with the study of data collection, data analysis, data interpretation, data presentation, and data organization. Statistics is mainly used to acquire a better understanding of data and to focus on specific applications. Also, Statistics is the process of gathering, assessing, and summarising data in a mathematical form.
Mathematically there are two approaches for analyzing data in statistics that are widely used:
Descriptive Statistics -
Using measures of central tendency and measures of dispersion, the descriptive technique of statistics is utilized to describe the data collected and summarise the data and its attributes.
Inferential Statistics -
This statistical strategy is utilized to produce conclusions from data. Inferential statistics rely on statistical tests on samples to make inferences, and it does so by discovering variations between the two groups. The p-value is calculated and differentiated to the probability of chance() = 0.05. If the p-value is less than or equivalent to, the p-value is considered statistically significant.