For caries prevention, a 0.2% sodium fluoride mouth rinse is typically recommended for use once weekly. This regimen provides sufficient fluoride exposure to strengthen tooth enamel without causing adverse effects.

In a double-blind study, neither the participants nor the experimenters know who is receiving the treatment or the placebo. This is to prevent any bias in the study results due to the expectations of the participants or the researchers. The statement that the investigator can omit data that fails to support the hypothesis is not correct; data should be analyzed as is to maintain the integrity of the study.

A higher drop-out rate can reduce the power of a study, as it leads to a smaller sample size and potentially less reliable results. To maintain the statistical significance and power of the study, a larger sample size must be enrolled initially to account for the expected number of participants who will not complete the study. Other factors that influence sample size include the incidence of the disease, the significance level, and the size of the expected treatment effect, but the question specifically asks about the impact of an increasing drop-out rate.

Primary prevention involves intervening before a lesion occurs to prevent the disease from developing. This includes actions like brushing with fluoride toothpaste, using fluoride mouth rinses, and maintaining a balanced diet to prevent dental caries.

Group discussion because participants get chances to express thier views Idea panel discussion : 4-8 people talk abt a topic in front of large group. symposium:series of speeches on a selected subject, no discussion. group discussion :considered a very effective method of health edu if the group consists of not less than 6 and not more than 20 persons. workshop:usually lasts for few days wher people get together and work in different groups and discuss problem of concern it can be called a problem solving method.