Non-melanoma skin cancer which includes basal cell (BCC) and squamous cell (CSS)
ID: 3183547 • Letter: N
Question
Non-melanoma skin cancer which includes basal cell (BCC) and squamous cell (CSS) carcinoma, is the most common type of cancer. Residents of Queensland experience a significantly greater incidence of these cancers than other Australians. Although not usually life-threatening, non-melanoma cancers result in substantial morbidity and treatment expense. A history of actinic keratoses (AK), a type of skin lesion, has generally been accepted as a marker for identifying individuals at increased risk of skin cancer. Often AK lesions progress to non-melanoma skin cancer. Those individuals with a history of AK, but few if any non-melanoma skin cancers, are considered to be at moderate risk. Also, fair-skinned, older people with a long history of sun exposure are more at risk for skin cancer. Results from clinical and laboratory studies suggest that vitamin A and other have a preventative effect against cancer in epithelial tissues such as skin. However, these studies have involved only small numbers of subjects and have not produced reliable estimates of the vitamin A effect in the primary prevention of human skin cancer. A five-year clinical trial is being proposed in Queensland to evaluate the effectiveness of vitamin A supplementation to reduce the risk of non-melanoma cancer for individuals at moderate risk. The research hypothesis is that vitamin supplementation reduces the incidence of skin cancer in moderate-risk individuals with a history of at least ten actinic keratoses. A double-blind, comparative experiment involving a treatment and placebo group is planned. Based on available data, it has been estimated that the required sample size needed to achieve 80% power at the 1% level of significance is 1500 subjects in each group. What is meant by a placebo group in the context of this study? Carefully explain why it is important to have a placebo group. A number of different response variables might be measured in this study. Define precisely a response variable which you believe would be appropriate. Define precisely the explanatory variable in this study.Explanation / Answer
Answer to part a)
Placebo group is a group that comes into picture when some treatment is applied and its effect has to be noted. In sucha situation some of the sampling units are kept in such a group on which no treatment is applied. This group is called pacebo group. The remaining sampling units are assigned to another gorup on which the treatment is applied. This group is called controlled group . Thus the observations are noted from both the groups , the placebo group serves as a reference point, and helps us observe if the readins of the controlled group are different from the placebo or not . if they aare different this implies that the treatment is effective. But if both the groups have same mean this implies that treatment had no effect.
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Answer to part b)
The most appropriate response variable is:
"Incident rate of skin cancer in moderate risk individuals"
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Answer to part c)
explanatory variable is the variable that helps predict the response variable. In this study there are various explanatory variable:
1. Geographical area : as stated the residents of queensland has significantly greater incidence rate
2. Skin color and exposure to sunlight also explains skin cancer
3. The deficiency of vitamin A may also explain the increase in skin cancer
Thus we can observe that the study tries to explain the cause of skin cancer, and lets us know all the valriables that help in predicting (explaining) the presence of skin cancer in people.
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