To check the effect of cold temperature on the elasticity of two brands of rubber bands, one box of brand a and one box of brand b rubber bands are tested. 10 bands from the brand a box are placed in a freezer for 2 hours and 10 bands from brand b are kept at room temperature. the amount of stretch before breakage is measure on each rubber band, and the mean for the cold bands is compared to the mean for the others. is this a good experimental design? a. no, because the means are not proper statistics for comparisonb. no, because more than 2 bands should be usedc. no, because more temperatures should be usedd. no, because temperature is confounded with brande. yes

Each of the following data sets has a mean of x = 10. (i) 8 9 10 11 12 (ii) 7 9 10 11 13 (iii) 7 8 10 12 13 (a) without doing any computations, order the data sets according to increasing value of standard deviations. (i), (iii), (ii) (ii), (i), (iii) (iii), (i), (ii) (iii), (ii), (i) (i), (ii), (iii) (ii), (iii), (i) (b) why do you expect the difference in standard deviations between data sets (i) and (ii) to be greater than the difference in standard deviations between data sets (ii) and (iii)? hint: consider how much the data in the respective sets differ from the mean. the data change between data sets (i) and (ii) increased the squared difference îł(x - x)2 by more than data sets (ii) and (iii). the data change between data sets (ii) and (iii) increased the squared difference îł(x - x)2 by more than data sets (i) and (ii). the data change between data sets (i) and (ii) decreased the squared difference îł(x - x)2 by more than data sets (ii) and (iii). none of the above