Question

Five students determined the solubility of KNO3 in water at 30degree celcius

a)can the outlier be discarded from this data set(perform the Q-test)

44.9 45.7 46.1 45.8 46.0 (gKNO3/100g H2O)

b)determin the mean, standard deviation and confidence interval(at the 90% level ) of the data set

Answer 1

A) Q test:

Consider the data points as given 44.9, 45.7, 46.1, 45.8, 46.0

Now arrange the data in increasing order as follows

44.9, 45.7, 45.8, 46.0, 46.1

We hypothesize that 44.9 is an outlier. Calculate Q:

Q = (45.7-44.9) / (46.1-44.9)
Q = 0.67

At 90% confidence level and 5 observations
Qexp = 0.667 > Qtable = 0.642

so we conclude 44.9 is an outlier and can be discarded from the data set

Table of critical values of Q

B) Mean

= (45.7+ 45.8+ 46.0+ 46.1)/4

= 45.9

Standard deviation

= 0.18257