The Nurses Health Study has been collecting health and behavioral data every two years since 1976 using the same very large representative sample of female registered nurses in the United States In 2004 a measure of optimism was included in the questionnaire filled by 70 021 study participants A 2017 publication evaluated the association between optimism and mortality from heart disease in the 8 years following the optimism questionnaire It reported that the proportion of women dying from heart disease was significantly smaller for the group of women with the highest optimism level than for the group of women with the lowest optimism level statistical inference 1 What type of study is this a case control observational s 2 Can we conclude from the 2017 study that high optimism helps prevent death from heart disease among female nurses in the United States Yes because the study has a v