A toy projectile launcher (12) that launches projectiles (14) with elastic elements (42). Each elastic element (42) is designed to be easily replaced on the projectile launcher (14). Each replaceable elastic element (42) has two ends (44, 46). An anchor block (54) is provided that receives and retains at least one of the two ends (44, 46). The anchor block (54) is received within an anchor receptacle (52). A locking mechanism (50) is used that selectively locks the anchor block (54) within the anchor receptacle (52). The elastic elements (42) extend from the anchor receptacles (54) and present projectile engagement structures (16, 18) that can be hooked by the toy projectile (14) being launched.

A toy bow assembly (10) that is used to launch toy projectiles (14). The toy bow assembly (10) includes a bow structure (12) having a first arm section (28) and a second arm section (30). Both the first arm section (28) and the second arm section (30) have sheathed areas (37) (43) that are protected from ambient light. A central area (15) is disposed between the first arm section (28) and the second arm section (30). A first elastic element (18) extends through the first sheathed area (37) into the central area (15), wherein the first sheathed area (37) shields the first elastic element (18) from exposure to ambient light. Likewise, a second elastic element (18) extends through the second sheathed area (43) and into the central area (15), wherein the second sheathed area (43) shields the second elastic element (18) from exposure to ambient light.

A toy bow assembly (10) that is used to launch toy projectiles (14). The toy bow assembly (10) includes a bow structure (12) having a first, arm section (28) and a second arm section (30), Both the first arm section (28) and the second arm section (30) contain at least one translucent area (49). Lights (51) are disposed within both the first arm section (28) and the second, arm section (30). The lights (51) internally illuminate the translucent areas (49) of the first arm section (28) and second arm section (30) when activated. An activation switch (55) is disposed on the bow structure (12) for selectively activating- and deactivating the lights (51).

A toy launching assembly (10) for pneumatically launching toy projectiles (20). The toy launching assembly (10) has a base structure (12) that contains an open port (50). A tube carousel (14) rotates atop the base structure (12). The tube carousel (14) holds a plurality of launching tubes (16). A pulse of air is generated by rapidly compressing an air bladder (18). The pulse of air travels through an air hose (19) to the base structure (12). Within the base structure (12), the pulse of air directed to the open port (50) under the tube carousel (14). An indexing mechanism (52) is used to rotates the tube carousel (14) and sequentially positions one of the launching tubes (16) over the open port (50) each time the air bladder (18) is sufficiently compressed.

A toy projectile launcher assembly (10) has the form of a crossbow. The crossbow only launches the safety projectiles (40) that are provided. The launcher body (12) has a handle (24) at a first end and diverging support arms (18) at an opposite second end. An adjustment mechanism (70) is contained within the launcher body (12) for selectively adjusting the length of the launcher body (12). Bow arms (30) are attached to the support arms (18). The bow arms (30) pivot from retracted positions to extended positions when a projectile (40) is loaded into the toy crossbow. The toy crossbow has elastic loops (36) that can only engage specialized safety projectiles (40). Furthermore, the trigger mechanism (60) can only engage the safety projectiles (40) provided with the toy.

Missing data can result in biased estimates of the association between an exposure X and an outcome Y. Even in the absence of bias, missing data can hurt precision, resulting in wider confidence intervals. Analysts should examine the missing data pattern and try to determine the causes of the missingness. Modern software has simplified multiple imputation of missing data and the analysis of multiply imputed data to the point where this method should be part of any analyst's toolkit. Multiple imputation will often, but not always, reduce bias and increase precision compared with complete-case analysis. Some exceptions to this rule are noted in this review. When describing study results, authors should disclose the amount of missing data and other details. Investigators should consider how to minimize missing data when planning a study.

The risk ratio can be a useful statistic for summarizing the results of cross-sectional, cohort, and randomized trial studies. I discuss several methods for estimating adjusted risk ratios and show how they can be executed in Stata, including 1) Mantel-Haenszel and inverse-variance stratified methods; 2) generalized linear regression with a log link and binomial distribution; 3) generalized linear regression with a log link, normal distribution, and robust variance estimator, 4) Poisson regression with a robust variance estimator; 5) Cox proportional hazards regression with a robust variance estimator; 6) standardized risk ratios from logistic, probit, complementary log-log, and log-log regression; and 7) a substitution method. Advantages and drawbacks are noted for some methods.

When a study outcome is rare in all strata used for an analysis, the odds ratio estimate of causal effects will approximate the risk ratio; therefore, odds ratios from most case-control studies can be interpreted as risk ratios. However, if a study outcome is common, the odds ratio will be further from 1 than the risk ratio. There is debate regarding the merits of risk ratios compared with odds ratios for the analysis of trials and cohort and cross-sectional studies with common outcomes. Odds ratios are conveniently symmetrical with regard to the outcome definition; the odds ratio for outcome Y is the inverse of the odds ratio for the outcome not Y. Risk ratios lack this symmetry, so it may be necessary to present 1 risk ratio for outcome Y and another for outcome not Y. Risk ratios, but not odds ratios, have a mathematical property called collapsibility; this means that the size of the risk ratio will not change if adjustment is made for a variable that is not a confounder. Because of collapsibility, the risk ratio, assuming no confounding, has a useful interpretation as the ratio change in average risk due to exposure among the exposed. Because odds ratios are not collapsible, they usually lack any interpretation either as the change in average odds or the average change in odds (the average odds ratio).

A greenhouse (10) comprising a growing section (16) and a climate control system (12) adjacent to the growing section (16). The climate control system (12) controls the environment within said growing section (16) by flowing ambient air from outside the greenhouse (10) into the growing section (16), re-circulating air from the growing section (16) back into the growing section (16), or a combination thereof. A method for controlling the temperature within a greenhouse growing section, comprises flowing air into the growing section from outside the greenhouse to reduce the temperature in the growing section. Warm air is flowed into the growing section to increase the temperature in the growing section, air within the growing section is re-circulated when the temperature therein is at the desired level.