<prompt> The PEFR of a group of 11 year old girls follow a normal distrubution with mean 300 1min and standard deviation 20 1min -About 95 of the girls have PEFR between 260 and 340 1min.The girls have healthy lungsAbout 5 of girls have PEFR below 260 1min.All the PEFR must be less than 340 1min.  <response>: 1 SD includes 68 of values2 SD includes 95 of values3 SD includes 99.7 of valuesIn this questionMean PEFR 300 LminSD 2 LminArea around 1SD on either side of mean x 1SD will include 68 of values, i.e.x 1SD30020So, 68 of girls have PEFR between 280 320 Lmin.Area around 2SD on either side of mean x 2SD will include 95 of values, i.e.x2SD30040So, 95 of girls have PEFR between 260 340 Lmin.Area around 3SD on either side of mean x 3SD will include 99.7 of values, i.e. -x 3SD 300 60So, 99.7 of girls will have PEFR between 240 360 Lmin. 