Statistics - Mean and Standard Deviation for Grouped Data

Statistics - Mean and Standard Deviation for Grouped Data

Secondary 4

The mass \(x\) grams of each of \(90\) oranges of variety \(A\) were recorded. The data obtained was illustrated as shown in the table.

Mass \(x\) gramsNo. of oranges
\(60 < x \le 70\)\(1\)
\(70 < x \le 80\)\(3\)
\(80 < x \le 90\)\(9\)
\(90 < x \le 100\)\(28\)
\(100 < x \le 110\)\(37\)
\(110 < x \le 120\)\(8\)
\(120 < x \le 130\)\(4\)
  1. Find the mean and standard deviation for the above data.
  2. In an another variety, variety \(B\), of the \(90\) oranges, the lightest orange has the mass \(55\) grams and the heaviest orange has the mass \(138\) grams. The median, lower quartile and upper quartile are \(102\) grams, \(93\) grams and \(109\) grams respectively. Draw the box-whisker diagram for this data.
  3. If you were to buy some oranges, which variety would you buy? Explain your answer.

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Answer:(a) mean \(100\) g, standard deviation \(11.1\) g (b) \(55,93,102,109,138\) (c) Variety A (more consistent)

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