Answer:
z -score = 0.0459
Step-by-step explanation:
Given that:
the number of children with food allergies at a sample of elementary schools: 3, 9, 5, 5, 14, 10, 5, 11, 9, 6, 1, 8, 10, 7, 9, 13, 18, 9, 8, 11, 9, 7, 6, 14, 12.
The objective is to find the z- score , but before we can do that , we need to determine the mean and the standard deviation of the sample.
Mean = sum of the sample/ total number of the sample
Mean = (3+9+ 5+ 5+ 14+ 10+ 5+ 11+ 9+ 6+ 1+ 8+ 10+ 7+ 9+13+ 18+ 9+ 8+11+ 9+ 7+ 6+ 14+ 12)/25
Mean = 219/25
Mean = 8.76
Standard deviation = [tex]\sqrt{\dfrac {\sum (x_i - \mu)^2}{N}}[/tex]
Mean (in order )= 1, 3,5,5,5,6,6,7,7,8,8,9,9,9,9,9,10,10,11,11,12,13,14,14,18)
Standard deviation = [tex]\sqrt{\dfrac { (8.76 - 1)^2}{25} + \dfrac { (8.76 - 3)^2}{25} +\dfrac { (8.76 - 5)^2}{25} +...+ \dfrac { (8.76 - 18)^2}{25} }[/tex]
Standard deviation = 5.2174
The standard z score formula is:
[tex]z = \dfrac{X- \mu}{\sigma}[/tex]
where X = median (13th observation ) = 9
[tex]z = \dfrac{9- 8.76}{5.2174}[/tex]
[tex]z = \dfrac{0.24}{5.2174}[/tex]
z -score = 0.0459
