RESEARCH STUDY 13.3: Dr.Anderson is a nutritionist who helps clients lose weight prior to surgery.She is working with W.J., a male client who is planning on undergoing a heart transplant.He currently eats more than 3,500 calories a day and has been asked by his doctor to cut the number of calories to about 1,800 (400 for breakfast, 600 for lunch, and 800 for dinner).She is curious as to whether a food journal will help W.J.reduce the number of calories he eats.A food journal is used to record everything a person eats to help patients be more aware of what they're eating.W.J.'s wife also recorded the food he consumed at each meal to have complete data before introducing the journal.Dr.Anderson decides to phase in the food journal gradually, initially only having W.J.record what he ate at breakfast during the first three days after baseline (days 4-6).During days 7-9, the journal is used at lunch, too, and during days 10-12, it also is used during dinner.The data for Dr.Anderson's study are below. Dr.Natchez, a colleague of Dr.Anderson, questions whether W.J.simply wrote down less in his journal as the study went on because he grew tired of completing this "measure." Dr.Natchez believes he has uncovered which of the following threats to internal validity?

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RESEARCH STUDY 13.3: Dr.Anderson is a nutritionist who helps clients lose weight prior to surgery.She is working with W.J., a male client who is planning on undergoing a heart transplant.He currently eats more than 3,500 calories a day and has been asked by his doctor to cut the number of calories to about 1,800 (400 for breakfast, 600 for lunch, and 800 for dinner).She is curious as to whether a food journal will help W.J.reduce the number of calories he eats.A food journal is used to record everything a person eats to help patients be more aware of what they're eating.W.J.'s wife also recorded the food he consumed at each meal to have complete data before introducing the journal.Dr.Anderson decides to phase in the food journal gradually, initially only having W.J.record what he ate at breakfast during the first three days after baseline (days 4-6).During days 7-9, the journal is used at lunch, too, and during days 10-12, it also is used during dinner.The data for Dr.Anderson's study are below.  Dr.Natchez, a colleague of Dr.Anderson, questions whether W.J.simply wrote down less in his journal as the study went on because he grew tired of completing this "measure." Dr.Natchez believes he has uncovered which of the following threats to internal validity?

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The Answer of RESEARCH STUDY 13.3: Dr.Anderson is a nutritionist who helps clients lose weight prior to surgery.She is working with W.J., a male client who is planning on undergoing a heart transplant.He currently eats more than 3,500 calories a day and has been asked by his doctor to cut the number of calories to about 1,800 (400 for breakfast, 600 for lunch, and 800 for dinner).She is curious as to whether a food journal will help W.J.reduce the number of calories he eats.A food journal is used to record everything a person eats to help patients be more aware of what they're eating.W.J.'s wife also recorded the food he consumed at each meal to have complete data before introducing the journal.Dr.Anderson decides to phase in the food journal gradually, initially only having W.J.record what he ate at breakfast during the first three days after baseline (days 4-6).During days 7-9, the journal is used at lunch, too, and during days 10-12, it also is used during dinner.The data for Dr.Anderson's study are below.  Dr.Natchez, a colleague of Dr.Anderson, questions whether W.J.simply wrote down less in his journal as the study went on because he grew tired of completing this "measure." Dr.Natchez believes he has uncovered which of the following threats to internal validity?