Robert stands three times on a pair of scales in a period of 5 minutes. The first time he weighs 92kg, the second time he weighs 102kg and the thrd time he weighs 95 kg. What conclusion can we draw based on this information on the pair of scales?
a. The pair of scales is reliable and valid
b. The pari of scales is not reliable.
c. The pair of scales is not valid.
d. The pair of scales is not reliable and not valid.