(20 PTS!!) The dot plot below shows the amount of time two random groups of students took to brush their teeth: Based on visual inspection of the dot plots, which of the following groups, if any, shows a greater average time required to brush their teeth? Group R Group S Both groups show about the same average time. No conclusion about average time can be made from the data.

• santanab021435: the answer would be "both groups show about the same average time"
• erinna:

  Answer:

  The correct option is C.

  Step-by-step explanation:

  In a dot plot, the number of dots above a number represents the frequency of that number.

  From the given dot plot it is clear that number of dots for group R is 21 and the time taken by the students of groups R are

  45, 50, 50, 55, 60, 60, 70, 75, 80, 85, 90, 90, 95, 100, 100, 105, 110, 110, 115, 120, 120

  The average of the data is

  [tex]Average=\frac{\sum x}{n}[/tex]

  [tex]Average=\frac{45+50+50+55+60+60+70+75+80+85+90+90+95+100+100+105+110+110+115+120+120}{21}[/tex]

  [tex]Average=\frac{1785}{21}[/tex]

  [tex]Average=85[/tex]

  From the given dot plot it is clear that number of dots for group S is 17 and the time taken by the students of groups S are

  50, 55, 60, 60, 65, 70, 70, 80, 90, 90, 95, 100, 105, 110, 110, 115, 120

  [tex]Average=\frac{50+55+60+60+65+70+70+80+90+90+95+100+105+110+110+115+120}{17}[/tex]

  [tex]Average=\frac{1445}{17}[/tex]

  [tex]Average=85[/tex]

  The average time of both groups are same.

  Since both groups show about the same average time, therefore the correct option is C.