Variance - practice problems
In statistics, a variance is the expectation of the squared deviation of a random variable from its mean.Instructions: Take your time with each problem and write out how you solved it step by step.
Number of problems found: 38
- Correct mean and CV
For a group of 100 students, the mean and coefficient of variation of their marks were found to be 60 and 25, respectively. Later, it was found that the scores 45 and 70 were wrongly entered as 40 and 27. Find the corrected mean and coefficient of variati - IQ scores
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. What percentage of the population scores higher than 125 on an IQ test? - Variance formula
Find the variance of 10,10,10,20,20,30. - Coefficient of skewness For the data set whose Karl Pearson's Coefficient of skewness = -2.25, variance is 16, and Mean is 35, then its median value will be:
- A sample variance
Calculate the value of the sample variance. −8,−8,−3,13,4,−8,10,8 - The number 7
The number of faulty units in a carton of a particular product is known to be normally distributed with a Mean of 10 and a variance of 25. What portion of a given carton of the product is expected to contain___ faulty units? (I) less than 8 (ii) more than - CFO Director
The financial director has determined the following profitability scenarios for the profitability of the new branch of the company: Profit of 5 million CZK with probability 0.1. Profit of 3 million CZK with probability 0.3. Profit of 1 million CZK with pr - Family height statistics
The average height of a member of a family of five is 1.5m, the mode of their height is 1.2m and the median is 1.6m. Find out the heights of individual members of this family if you know that they are integers in dm. - Statistical file characteristics Determine the median, mode, arithmetic mean, variance, standard deviation, range of variation, and coefficient of variation of the character x in the statistical file: 2x 9, 7x 10, 9x 11, 11x 15, 15x 17, 16x 19, 13x 21, 10x 25, 9x 29, 4x 32
- Grouped data range In grouped data classes such as 10-15, 16-20, 21-25, 26-30 with the respective frequencies of each class as 3, 5, 4, 3, then the range (range of variation) is: a. 15 b. 6 c. 20 d. 5
- Underweight babies
A sample of underweight babies was fed a special diet, and the following weight gains (lbs) were observed at the end of three months: 6.7, 2.7, 2.5, 3.6, 3.4, 4.1, 4.8, 5.9, and 8.3. Find the variance. (Round off to the nearest hundredths) - Summaries A specialist teacher observes the time taken by each of the students with learning disabilities to complete a psychological task. She summaries the times using the following: Time Taken(mins) ; 1-5; 6-10; 11-12; 16-20 No. of Student ; 2 ; 4 ; 12; 4 Using
- A sample
A sample of 10 randomly selected students revealed the following grades in Business Statistics first test (on a marking scale of 0 to 100): 79, 63, 60, 45, 55, 58, 59, 62, 40, 68. Examine the data using groups and presenting: a) the Histogram of the absol - Population variance
60% of students at a California community college will transfer to a college in the CSU system. The number of students in a sample who will transfer follows a binomial distribution. If eight students are randomly selected, find the population variance σ² - Unemployment rate
Over the last 16 years, the country's unemployment rate has changed according to the following frequency table: years of unemployment: 2 5 2 3 3 1 unemployment rate: 0.5 1 1.5 2 2.5 3 in % (percent). Determine the two-sided confidence interval for the var - Three sigma rule
The height of trees in a given stand is known to be a quantity with a normal probability distribution with a mean value of 15 m and a variance of 5 m². Determine the interval in which there will be tree heights in such a stand with a probability of 90% - Probability
In the elections, 2400000 voters out of a total of 6000000 voters voted for party Z. Let us randomly select three voters and consider the random variable ξ={number of voters for party Z in the sample of three voters}. Determine a) the probability distribu - Pupils - dataset
The following data on the height and the corresponding number of pupils were found in the measurement of 63 pupils: the height; number of pupils 159cm; 1 161cm; 1 162cm; 2 163cm; 1 164cm; 2 165cm; 2 166cm; 3 167cm; 2 168cm; 4 169cm; 3 170cm; 5 171cm; 6 17 - Marketing Year; money spent on advertising; profit 2008 2 12 2009 5 20 2010 7 25 2011 11 26 2012 15 40 1. draw a scatter diagram depicting the data. 2. calculate the Pearson's correlation coefficient. 3. determine the linear regression equation.
- IQ Intelligence quotient
Intelligence quotient (IQ) is a standardized score used as the output of standardized intelligence psychological tests to quantify a person's intelligence with the rest of the population (respectively, to a given group). Intelligence has an approximately
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