**GlassRI 02:
Grouping refractive index data by SKM2 using a calculator
**

Assume that five fragments have been recovered from a suspect. These fragments have RI values (each the average of several GRIM measurements) given by:

1.52428 |
1.52419 |
1.52430 |
1.52420 |
1.52427 |

Six control samples submitted have RI values of

1.52419 |
1.52421 |
1.52414 |
1.52422 |
1.5242 |
1.52426 |

which have
a mean value = 1.52420 and
standard deviation = 3.93×10^{-05}

Group the recovered samples "by eye" and check the validity of the grouping by calculating the value l

Use the standard deviation of the control as an estimate for the standard
deviation of the recovered group.

Video Answer:
l^{*}
= 8.28, 1 group