Standard deviation - math problems

Number of problems found: 40

  • Manufacturing company
    statistics A random sample of 8 manufacturing companies is selected from a population of manufacturing companies. The market values (in millions of rands) of these 8 manufacturing companies are: 17 65 117 206 172 181 221 94 What is the lowest and highest market valu
  • A professor
    skola A professor in a typing class found out that the average performance of an expert typist is 85 words per minute. A random sample of 16 students took the typing test and an average speed of 62 words per minute was obtained with a standard deviation of 8. C
  • Unemployment rate
    normal_d 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 unemploymen rate: 0.5 1 1.5 2 2.5 3 in % (percent). Determine the two-sided confidence interval for the vari
  • Chi square
    chi_squared A manufacturer of phone batteries claims that his batteries' lives are approximately normally distributed with a standard deviation equal to 0.9 years. If a random sample of 10 of these batteries has a standard deviation of 1.2 years. Do you think that th
  • Confidence Interval
    normal_d The average grade of 50 students senior students in a statistics class is 85 with a standard deviation of 10.2 while a group of 60 senior students got an average of 80 with a standard deviation of 8.9, can the difference in the mean grade be attributed to
  • Performance comparing
    statistics A standardized test was administered to thousands of students with a mean score of 85 and a standard deviation of 8. A random sample of 50 students were given the same test and showed an average score of 83.20. Is there evidence to show that this group ha
  • Three sigma rule
    stromy 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%
  • A machine
    rods_normal A machine produces steel rods of normally distributed length; the mean length and the standard deviation being 50.0 cm and 0.5 cm respectively. The rods do not conform to safety standards if they are either shorter than 49.1 cm or longer than 50.7 cm in l
  • Five number summary
    statistics Find the five-number summary for these data and make a boxplot. 14,5,12,19,2,35,5,4,3,7,5,8
  • Confidence interval
    normal_d A food testing laboratory in Abu Dhabi has been commissioned to carry out an estimate of the amount of olive oil contained in 1-gallon tins purchased from a range of international olive oil producers. The manufacturers state that the standard deviation of
  • 5-number summary
    statistics Given the following 5-number summary: 11, 19, 24, 30, 48 which of the statistics cannot be determined?
  • Bivariate data set
    statistics Here is a bivariate data set in which you believe y to be the response variable. x y 51.4 44.8 60.2 46.6 60.1 46.8 45.8 46.3 37.4 41.8 72.4 52.5 60 48.2 67.5 49.5 60.9 49.8 51.1 45.7 62.7 49.6 194.9 84.2 Make a scatter plot of this data. Which point is an
  • Dataset:
    statistics Dataset: 35 22 18 54 22 46 28 31 43 22 14 17 25 19 33 14. 1 Group the data into a grouped distribution using 6 classes of equal width. 2. Determine the mean, median, and mode using the raw data. 3. Draw an Ogive curve corresponding to the data and use it
  • Statistical survey
    statistics Write TRUE OR FALSE for each question: 1 Standard deviation is a measure of central location. 2. The most frequent observation in a data set is known as the mode. 3 The most passive method of data collection is observation. 4 Access time for secondary dat
  • A mountain climber
    rope_normal_stdev A mountain climber plans to buy some rope to use as lifeline. Which of the following would be the better choice? Explain your choice. Rope A: Mean breaking strength:500lb; standard deviation of 100lb Rope B: Mean breaking strength: 500lb; standard deviati
  • Tallest people a
    normal_d As a group, the Dutch are amongst the tallest people in the world. The average Dutchman is 184 cm tall. If a normal distribution is appropriate, and the standard deviation for Dutchmen is about 8 cm, what is the percentage of Dutchmen who will be over 2 m
  • The raw
    statistics The raw data presented here are the scores (out of 100 marks) of a market survey regarding the acceptability of new product launched by a company for random sample of 50 respondents: 40 45 41 45 45 30 30 8 48 25 26 9 23 24 26 29 8 40 41 42 39 35 18 25 35
  • Statistical XY file
    trendline Year; money spent on advertising; profit (three values each row) 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 equat
  • Marketing
    statistics 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.
  • Complaints
    statistics The table is given: days complaints 0-4 2 5-9 4 10-14 8 15-19 6 20-24 4 25-29 3 30-34 3 1.1 What percentage of complaints were resolved within 2weeks? 1.2 calculate the mean number of days to resolve these complaints. 1.3 calculate the modal number of day

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