Seat belt use and Injuries

We have column 'Observed'. We can calculate column 'Expected' using the historical percentages as follows: Stat > Column Statistics, Input variable: Observed show there were 525 people involved in car accidents
Calc > Calculator, Store in: Expected, Expression: 'Historical Percentages'/100*525

Step 1: Graph
Graph > Bar Chart > Values from a Table, Two-way table, Cluster, Graph Variables: Observed Expected, Row labels: Bloat, check Rows are outermost ..

Step 2: Table
Required Treatment Observed Expected
None 316 257.25
Treated and released 154 204.75
Treated and admitted 34 42.00
Died 9 5.25
Unknown 12 15.75

Step 3: Test

Make a new column, called T, with Calc - Calculator - Expression
SUM(('Observed' - 'Expected')**2 / 'Expected')
Calc - Probability Distributions - Chi Square
Input Column: T
Degrees of Freedom: #of classifications - 1 = 4
p value = 1 - P( X <= x )

1) α=0.05
2) H0: Theory is true (historical precentages are still true, seat belt laws make no difference)
3) Ha: Theory is false (historical precentages are no longer true, seat belt laws do make difference)
4) p = 1-1 = 0.0 < α
5) We reject H0, seat belt laws do make difference.