Agroup of researchers conduct a study to increase exercise among older women to prevent bone loss (osteoporosis). during the time of the study the local pbs station introduces a series of shows on osteoporosis prevention. this is an example of:
temporal ambiguity
threat of history
threat of maturation
mortality

Threat of history

This takes into consideration various events that happen or take place outside the domain of the study that further may affect the reaction or views of an individual and therefore affect their effect on the experiment. Some of the examples of these events are political change, natural disasters that can affect the individuals’ response to the study making it difficult to conclude the experiment.

$450 is the answer.

step-by-step explanation:

30% of 450 = 135

450-135=315