Statistics Measures of Centrality and Spread
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Questions and Answers

What is the mode in the discrete data set of idle days: 2, 6, 2, 4, 1, 4, 3, 1, 1?

  • 2
  • 3
  • 4
  • 1 (correct)
  • Which measure of centrality represents the middle value of a data set when ordered?

  • Median (correct)
  • Mean
  • Mode
  • Range
  • In the calculation of the mean, what does the symbol $ ext{∑}$ represent?

  • Average value
  • Frequency of values
  • The sum of all values (correct)
  • The number of data points
  • What type of data is characterized by individual values such as people or cars?

    <p>Discrete data</p> Signup and view all the answers

    What is the mean of the number of idle days based on the grouped data for 95 cars?

    <p>2.30</p> Signup and view all the answers

    Which of the following correctly describes continuous data?

    <p>Ranges rather than distinct values</p> Signup and view all the answers

    What is the median of the discrete data set: 1, 1, 1, 2, 2, 3, 4, 4, 6?

    <p>2</p> Signup and view all the answers

    How is the mean calculated for grouped data?

    <p>Sum of the product of frequencies and values / Total frequency</p> Signup and view all the answers

    What is the inter-quartile range of idle days for the 95 staff cars?

    <p>2 days</p> Signup and view all the answers

    What is the semi-inter-quartile range for the idle days of the staff cars?

    <p>1 day</p> Signup and view all the answers

    What is the standard deviation for the sample of 95 staff cars?

    <p>1.345</p> Signup and view all the answers

    If the range of idle days is from 0 to 6, what is the total range?

    <p>6 days</p> Signup and view all the answers

    What is the mid-value of the value range for users of £63 but less than £64?

    <p>63.5</p> Signup and view all the answers

    How many users fall into the range of £62 but less than £63?

    <p>6 users</p> Signup and view all the answers

    What is the total count of car users in the provided data for the fuel invoices?

    <p>34 users</p> Signup and view all the answers

    What is the value of 'fx' for the mid-value of £60.5 per 5 users?

    <p>302.5</p> Signup and view all the answers

    What is the modal class of car values based on the provided data?

    <p>£64 but &lt; £65</p> Signup and view all the answers

    What is the mean value of the car prices based on the data?

    <p>£62.97</p> Signup and view all the answers

    How is the standard deviation for a population calculated?

    <p>By taking the square root of the variance.</p> Signup and view all the answers

    What does the semi-inter-quartile range represent?

    <p>Half the range of the middle half of the ordered data.</p> Signup and view all the answers

    In the example given, what is the range of idle days for the nine members of staff?

    <p>5 days</p> Signup and view all the answers

    What represents the frequency in the context of standard deviation calculation?

    <p>The number of occurrences of each specific data value.</p> Signup and view all the answers

    What is the inter-quartile range for the example of idle days provided?

    <p>3 days</p> Signup and view all the answers

    Which statistical measure reflects the average spread of the data around the mean?

    <p>Standard deviation</p> Signup and view all the answers

    When using sample standard deviation, what adjustment is made to the sample size in the denominator?

    <p>The sample size is decreased by one.</p> Signup and view all the answers

    Which measure of spread would be appropriate if all data points are known?

    <p>Population standard deviation</p> Signup and view all the answers

    What is the semi-inter-quartile range for the given data?

    <p>£1</p> Signup and view all the answers

    Which car value has the highest number of users?

    <p>64.5</p> Signup and view all the answers

    What is the total number of users in the sample?

    <p>34</p> Signup and view all the answers

    What does the histogram indicate about the frequency of car mileages in the range of 120 to 130 miles?

    <p>There were 10 cars in that mileage range</p> Signup and view all the answers

    From the summarized statistics, which value is used as a population estimator?

    <p>£1.958</p> Signup and view all the answers

    How is the mode estimated using the histogram?

    <p>By finding the highest frequency column</p> Signup and view all the answers

    Which range of car values includes a total of 4 users?

    <p>61 but &lt; 62</p> Signup and view all the answers

    What is the estimated mode of car mileages according to the histogram?

    <p>146 miles</p> Signup and view all the answers

    What does the inter-quartile range indicate in a data set?

    <p>The difference between the upper quartile and the lower quartile</p> Signup and view all the answers

    Which statistic should be used for ordinal data to represent variability?

    <p>Inter-quartile range</p> Signup and view all the answers

    If the median value is $146$ miles, what does this indicate about the data set?

    <p>50% of the data values are below 146 miles</p> Signup and view all the answers

    What is the upper quartile value in the given data set?

    <p>156 miles</p> Signup and view all the answers

    Which measure is most appropriate for representing the central tendency of interval data?

    <p>Mean</p> Signup and view all the answers

    Study Notes

    Numerical Data Summary

    • Data can be summarised by two parameters: measures of centrality and measures of spread.
    • Measures of Centrality indicate a typical or central value.
      • Mode: The most frequently occurring value in a dataset.
      • Median: The middle value of a dataset ordered from smallest to largest.
      • Mean: The arithmetic average of all values in a dataset.
    • Measures of Spread show how widely the data is distributed around its center.
      • Range: The difference between the largest and smallest values.
      • Inter-quartile Range (IQR): The range of the middle 50% of the data.
      • Semi-inter-quartile Range (SIQR): Half the value of the IQR.
      • Standard Deviation: A measure of the average deviation of data points from the mean.
    • Standard Deviation can be calculated for both populations and samples.
      • Population Standard Deviation (σ): A measure of the spread of data in an entire population.
      • Sample Standard Deviation (s): An estimate of the population standard deviation based on a sample of data.
    • The choice of the most appropriate measure of centrality and spread depends on the type of data.
      • For ordinal data, use the median and IQR.
      • For interval or ratio data, use the mean and standard deviation.
    • Graphical representations of data can be used to estimate summary statistics.
      • Histograms can be used to estimate the mode.
      • Cumulative frequency diagrams (ogives) can be used to estimate the median and interquartile range.

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    Description

    This quiz covers the key concepts of measures of centrality and spread used in summarizing numerical data. You'll explore the mode, median, and mean, along with range, inter-quartile range, and standard deviation. Test your understanding of these essential statistical measures and their applications.

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