An experiment includes a treatment condition, a no-treatment control, and a placebo control. Which two conditions should be compared to determine the size of the effect that is actually caused by the treatment?

A74-year-old woman, who has been followed for the past 25 years for chronic obstructive pulmonary disease comes to the ed complaining of 48 hours of temperature to 38.6 c and worsening shortness of breath. she has a chronic productive cough, which has become more copious. on physical examination, she has rhonchi and increased fremitus in the posterior mid-lung field. a gram's stain reveals many epithelial cells and multiple gram-positive and gram-negative organisms; no neutrophils are seen. which of the following is the most likely organism causing the symptoms? - escherichia coli- haemophilus influenzae- klebsiella pneumoniae- mycobacterium tuberculosis- mycoplasma pneumoniae