Does the position of the rider (driver or passenger) on the moped affect their chances of sustaining a head injury? (Hint – first calculate the crude odds ratio for the association between moped...

Does the position of the rider (driver or passenger) on the moped affect their chances of sustaining a head injury? (Hint – first calculate the crude odds ratio for the association between moped position and head injury and then consider whether this could be confounded by helmet use.)