Sarah’s organic soap (q18 – q20) sarah’s organic soap company makes four kinds of organic liquid soap - regular, lavender, citrus, and tea tree. demand for the four scents are 150, 120, 75 and 50 kgs per hour, respectively. sarah’s production process can produce any soap at the rate of 450 kgs per hour (i. e., processing time of 1 kg of soap is 1/450[kg/hour] = 0.00 [hour/kg]) but 1.5 hours are needed to switch between scents. during those switchover times, the process does not produce any soap. sarah wants to choose a production schedule that (i) cycles repeatedly through the four scents, (ii) meets the required demand and (iii) minimizes the amount of inventory held. q20) again, assume that sarah needs 1,000 kgs of palm oil per day. sarah’s supplier is willing to sell her palm oil at a 5% discount if she purchases 10,000 kgs at a time. if she were to purchase 10,000 kgs per order, what would be the total daily cost (in $) that includes the daily inventory holding cost, daily ordering cost, and daily purchasing cost?

Reliability and validity reliability and validity are two important considerations that must be made with any type of data collection. reliability refers to the ability to consistently produce a given result. in the context of psychological research, this would mean that any instruments or tools used to collect data do so in consistent, reproducible ways. unfortunately, being consistent in measurement does not necessarily mean that you have measured something correctly. to illustrate this concept, consider a kitchen scale that would be used to measure the weight of cereal that you eat in the morning. if the scale is not properly calibrated, it may consistently under- or overestimate the amount of cereal that’s being measured. while the scale is highly reliable in producing consistent results (e.g., the same amount of cereal poured onto the scale produces the same reading each time), those results are incorrect. this is where validity comes into play. validity refers to the extent to which a given instrument or tool accurately measures what it’s supposed to measure. while any valid measure is by necessity reliable, the reverse is not necessarily true. researchers strive to use instruments that are both highly reliable and valid.