Statistical Methods in Medical Research

A child-resistant, two-piece closure which may be attached to a container by conventional capping machines. An inner member is formed with a circular top panel having a depending skirt integrally molded therewith. The depending skirt is threaded on its inner surface for engagement with a conventional threaded container finish. The exterior surface of the depending skirt has a plurality of splines about its entire circumference. A plurality of vertical lugs project from and are integrally molded with the top panel. An outer member is likewise formed with a circular top panel and a depending skirt. Integrally formed with the interior of the outer member top panel are a plurality of downwardly extending leaf spring members. The inner surface of the outer member depending skirt has integrally molded therein a plurality of splines extending about its entire circumference. The two members are assembled by pressing the inner member over a retention bead formed in the interior of the lower portion of the outer member depending skirt. The leaf spring members are inclined from the horizontal and will drivingly engage the vertical lugs to allow the assembled closure to be put on a container. However, the leaf spring members will slip over the lugs if one attempts to remove the closure, thus allowing the outer member to rotate freely with respect to the inner member. To remove the closure, the outer member must be pressed down, overcoming the bias of the leaf spring members, to bring the splines of the inner and outer members into driving inter-engagement.