Solutions to two common time series graphing problems are presented. The revised graph in thefirst group shows the diference between Q criterion level and an actual level offinancial per fomme; the second shows the behavior ofstatewide student cohorts.

Time Series Graphs on Financial Performance and Cohort Dropout Rates Kathleen Sullivan

The graphs presented in this chapter are from recent reports to the Mlsslssippl legislature. They illustrate solutions to problems that are common when reportmg information on a time series. One problem entails showing a differ- ence between two time-related trends over the same period. Column and line graphs are used to show the chfference between a criterion condition (in this case, payments that a small, rural utility must make to meet its financial obli- gations) and an actual or projected condition (amounts the distnct is likely to be able to pay). Ths example 1s comparable to illustrating a projection of a budget deficit or the gap between services needed and semces provided.

Another problem in presenting time series data entails showing effects of a program that 1s phased m (that IS, a€€ects drfferent groups at different times). Edu- cation programs are sometimes introduced this way Phased implementation can result in a distinctly different program experience €or each student cohort. In this chapter a line graph shows ddferences in program effects for a series of cohorts. This approach offers an altername to graphing averags that include data for par- ticipants and nonparticipants, which can mask program effects.

Evaluation Audiences Mississippi's Joint Legdative Committee on Performance Evaluation and Expenditure Review (PEER), created by statute in 1973, provides evaluative

Author's note: David J. Pray, Barbara Y. Hamilton, Stephen R Miller, H. L. Whiting, Mitchell H. Adcock, Max K. Arinder, and Ava L. Welborn helped develop the graphs and evaluation reports that are the subject of this chapter.

NEW DlRECTIONSMR EVALUATION, no. 73, S p h g 1997 0 JmSey-Bga Pubhhers 59

68 CREATING EFFECTIVE GRAPHS

that they masked any effect that the compulsory attendance law might have exerted on enrollment rates among the groups.

Impact of the Graph. PEER published the cohort graph in a report that also described serious problems in attendance officer program operations. The PEER staff presented the cohort dropout graph, like the utility district line graph, in a Powerfoint briefing to legislators. The graph contributed to a body of evidence that prompted legislators to discuss the need for a more effective approach to preventing absenteeism and dropping out among Mis- sissippi schoolchildren.

References Mississippi Joint Legislative Committee on Performance Evaluation and Expenditure

Review. Mississippi School Attendma Oflcers Propunr AJoiloint Study by the PEER Com- mittee and theJohn C. Stennis Institute ojGovernrnent Jackson: Mississippi Joint Legislative Committee on Performance Evaluation and Expenditure Review, 1994.

Mississippi Joint Legislative Committee on Performance Evaluation and Expenditure Review. A Rtvim if the Vidility ojthe Muntachie NuluraI Ga District and thc State’s Rela- tionship to the District. Jackson: Mississippi Joint Legislative Committee on Performance Evaluation and Expenditure Review. 1996.

KATHLEEN SULLIVAN i s evaluation division munugerfur the Mississippi Joint Legisla- tive Committee on Perjormance Evaluation and Expenditure Review.